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This text was first printed as “Design case historical past: the Commodore 64.” It appeared within the March 1985 problem of IEEE Spectrum. A PDF model is out there on IEEE Xplore. The diagrams and images of chips, circuit boards, and screens appeared within the authentic print model.

Charles Winterble, then director of worldwide engineering for Commodore, gave the go-ahead for the chip effort, and Charpentier’s group labored pretty independently till each chips have been completed in mid-November 1981.

At a gathering with Charpentier and Winterble late that month, Jack Tramiel, then president of Commodore, determined to not proceed with the online game. As a substitute, he determined, the chips would go right into a 64-kilobyte residence laptop to be launched on the Client Electronics Present in Las Vegas the second week of January 1982. The pc had but to be designed, however that was simply remedied.

In two days, the engineers laid out on paper the machine’s primary structure. Simply earlier than the brand new yr, they accomplished 5 working prototypes. Within the meantime, sufficient operating-system software program was copied and rewritten from the VIC-20 to provide satisfactory demonstrations of what the brand new machine might do. Following its enthusiastic reception on the Client Electronics Present, the Commodore 64 was rushed into manufacturing; quantity shipments started in August 1982 and have continued unabated.

Regardless of complaints about high quality management and the trade’s slowest disk drive, the Commodore 64 has been an unparalleled success, pushing a variety of its rivals out of the market. A part of the explanation for its success is the worth, which retains falling—from $595 at its introduction to $149 presently, for which the buyer will get graphics and sound equal to or higher than that offered by machines that price 5 instances as a lot.

Designing the subsequent nice chips

Within the late Seventies, MOS Expertise was a profitable semiconductor firm; its engineers had designed the favored 6502 microprocessor, and it manufactured a number of different solidly promoting merchandise. Commodore, a West Coast firm on the time, took over MOS in 1976—inflicting lots of the MOS engineers to stop when their inventory was purchased at 10 cents on the greenback—however MOS was allowed to function pretty autonomously.

In 1979 and 1980, recollects Charpentier, MOS Expertise developed the 6510 microprocessor—a minor revision of the 6502 with a further input-output port, the 6526 peripheral controller, quite a lot of read-only reminiscence (ROM) chips, and a 4-kilobit random-access reminiscence (RAM) chip. At the moment, MOS was supplying gear to Atari Inc., Common Electrical Co., Hewlett-Packard Co., and a variety of different shoppers, in addition to to Commodore.

When the choice was made to design the most recent in superior graphics and sound chips, step one was apparent: to search out what the present high-quality chips might do. In assembling his design staff, Charpentier recruited Robert Yannes, a younger engineer who had joined MOS in 1979 and had designed the VIC-20 at residence, from a spare prototype board. The staff spent about two weeks researching comparable chips industrywide.

“We seemed closely into the Mattel Intellivision,” recollects Winterble. “We additionally examined the Texas Devices 99/4A and the Atari 800. We tried to get a really feel for what these firms might do sooner or later by extrapolating from their present expertise. That made it clear what the graphics capabilities of our machine needed to be.”

The MOS designers freely borrowed concepts that they preferred—sprites from the TI machine, collision-detection strategies and character-mapped graphics from the Intellivision, and a bit map from their very own VIC-20. They then packed as lots of these concepts as they may right into a predefined space of silicon.

“Al [Charpentier] was given the liberty, inside a sure die measurement, to place in the whole lot he might, working backward inside the measurement we deliberate. When he ran out of registers he stopped,” mentioned Winterble. “We outlined prematurely the silicon measurement that may give a yield we have been prepared to reside with; at the moment, a die measurement that was affordable in 5-micrometer expertise was lower than 200 mils. Then we prioritized the want checklist from what should be in there to what ought to be in there to what we’d like to have, so the selections that have been wanted at varied factors grew to become pretty automated.”

9 months to first-pass silicon 

For 9 months, Charpentier labored with two draftsmen and one computer-aided-design operator on the graphics chip whereas Yannes labored with two different draftsmen and one CAD operator on the sound chip. They lacked fully the delicate design instruments of in the present day’s engineering workstations, however they’d one available design device discovered nearly nowhere else within the home-computer trade: a chip-fabrication line on the premises. With this, Winterble defined, a circuit buried deep contained in the chips might be lifted out and run as a take a look at chip, permitting thorough debugging with out concern for different components of the circuitry. David A. Ziembicki, then a manufacturing engineer at Commodore, recollects that typical fabrication instances have been a number of weeks and that in an emergency the captive fabrication facility might flip designs round in as little as 4 days.

The price of creating the Commodore 64: Nobody is aware of.

The price of creating the Commodore 64: Nobody is aware of. “I had no formal finances accountability,” mentioned Winterble, “aside from Jack [Tramiel] watching me. Jack mentioned that budgets have been a license to steal.” As a result of MOS Expertise’s fabrication facility was not operating at full capability, the gear used for C-64 take a look at chips and a number of passes of silicon would in any other case have been idle. “We have been utilizing individuals who have been there anyway,” mentioned Ziembicki. “You waste a bit little bit of silicon, however silicon’s fairly low cost. It’s solely sand.”

Though customized chips are normally thought of costly, the C-64 chips weren’t. Not solely have been improvement prices absorbed in firm overhead, however there was no markup to pay, as there would have been inf the chips had been constructed by one other firm. And yields have been excessive as a result of the chips have been designed for a mature semiconductor-manufacturing course of.

The sound chip was designed with 7-micrometer expertise, cutting down to six in locations. (In contrast, the customized chip for Atari’s Video Pc System, fabricated 4 years earlier, was constructed with 6-micrometer expertise.) Commodore’s video chip was designed with 5-micrometer options.

As a result of design time fairly than silicon was at a premium, the chips have been laid out merely fairly than compactly. “We did it in a really modular vogue,” mentioned Yannes. For instance, he famous, “the usual means of constructing oscillators is to construct one after which multiplex it till you’ve gotten as many as you want. We simply constructed an oscillator module and repeated it, as a result of that was a lot sooner than figuring out all of the timing for the multiplexer.”

“What was outstanding,” Winterble added, “was that 9 months later, once we got here out with the primary cross, it functioned aside from one unhealthy sprite.”

In November 1981, the chips have been full. The unique intent had been a recreation machine, however at this level the personal-computer market was starting to look promising. At a gathering of Charpentier, Winterble, and Tramiel, the choice was made to go for a private laptop. The following option to be made, in accordance with Charpentier, was between a 16-kilobyte and a 64-kilobyte machine, because the customized chips have been designed to deal with both possibility.

“Jack [Tramiel] made the wager that by the point we have been prepared to provide a product, 64K Rams can be low cost sufficient for us to make use of,” Charpentier mentioned.

When the design of the Commodore 64 started, the overriding targets have been simplicity and low price. The preliminary manufacturing price of the Commodore 64 was focused at $130; it turned out to be $135. The pc would use the identical case because the VIC-20 and the same-sized circuit board, to hurry improvement. “That wasn’t even a call,” mentioned Charpentier. “It was simply frequent sense. In case you’ve obtained a product that’s a winner, why change it?” To modify from the VIC-20 to the Commodore 64, the manufacturing group had solely to make the cartridge slot smaller, change the colour of the case, and design a brand new label.

Moreover, as an alternative of designing for efficiency first and value second, as many engineers are inclined to do, the small design staff at Commodore had price in thoughts from the start. Yannes, for instance, had made economic system his credo when he was an impecunious high-school scholar searching for components to construct a sound synthesizer. “Anytime I design one thing, I need to use the minimal variety of parts doable. It’s a private problem. If there’s a spare [logic] gate in a gate bundle, I’ll work to do away with the complete bundle, as a result of in working with a sure variety of chips, I ought to have the ability to burn up the whole lot that’s in them. The Commodore 64 was my try and construct absolutely the minimal system that might be constructed out of the video and sound chips put collectively.”

Joyful New Yr 1982!

Within the consumer-electronics trade, new merchandise are historically launched to distributors, sellers, the press, and the competitors twice a yr—throughout the first weekend in January and the primary weekend in June, on the Winter and Summer time Client Electronics Reveals (CESs).

“While you labored for Commodore,” mentioned Yannes, “you all the time needed to have one thing for the Winter CES.” The C-64 didn’t have a lot competitors on the winter present in 1982. Atari was nonetheless sowing its 400/800 laptop. Mattel launched the Aquarius laptop, and Spectravideo launched its laptop/recreation machine, each with restricted reminiscence and capabilities.

Ziembicki recalled, “All we noticed at our sales space have been Atari individuals with their mouths dropping open, saying, ‘How are you going to do this for $595?’”

“We have been successful,” Winterble added.

After the present, Commodore, which had a fame for typically exhibiting merchandise that by no means reappeared, needed to get the 64 into manufacturing rapidly. Just a few design modifications have been made to prepared the machine for manufacturing. “What’s within the 64 functionally is what I needed,’ Yannes mentioned. “What’s within the sound chip is what I needed, and what’s within the video chip is what Al [Charpentier] needed.”

Actually, mentioned Ziembicki, “after it lastly obtained into manufacturing, we seemed again and requested, why did we trouble altering it after January? It wouldn’t have offered one unit much less, and we’d have saved some huge cash on improvement prices.”

A number of the modifications have been pretty vital, however they might have created as many issues as they solved. The most important enchancment was to treatment “a hiccup” within the video chip, mentioned Winterble.

When Charpentier first designed the video chip, he defined, his aim was optimum efficiency in each black-and-white and coloration. Earlier video chips, reminiscent of these used within the Atari and the Apple, had a black-and-white frequency of seven.16 MHz—twice the tv color-clock frequency of three.58 MHz—however this might not squeeze sufficient characters on a line, and it additionally induced cross speak between the 2 alerts, inflicting an object to shift barely to the left or proper on the display screen relying on its coloration. After the January 1982 CES, when he noticed that 40 characters wouldn’t fairly match onto a TV display screen, Charpentier sped up the black-and-white clock charge and made the 2 clocks fully asynchronous. However because the coloration and black-and-white units of knowledge have been consistently altering section relative to one another, “the colour transitions have been implausible, however there was an general swimming impact,” he recalled. The answer was to place a phase-locked loop into the system so the colour and the black-and-white data would have a continuing relationship. This, Charpentier acknowledged, was “a Band-Support resolution.”

And that’s what it appears to be like like, in accordance with Craig Nelson, director of product improvement for Epyx Pc Software program of Sunnyvale, Calif. “It’s a very elegant circuit,” he mentioned, “aside from the phase-locked loop, which is simply caught in the midst of it.” (Commodore now says it has redesigned the chip to remove the issue.)

On account of the “Band-Support,” the colour data and the black-and-white data shift section by 180 levels in relation to one another on successive video fields fairly than altering section unpredictably. This conforms extra intently to the Nationwide Tv Programs Committee (NTSC) normal, which requires black-and-white data to have a clock charge that’s an odd harmonic of the color-clock charge, in order that the 2 routinely reverse their relationship each different area—one area in section, the subsequent area out of section. (Within the NTSC normal, colours are decided by the section distinction between the colour sign and a coloration reference sign transmitted originally of every line.)

On the time the usual was developed, generally accessible circuitry couldn’t fully separate the black-and-white data from the colour: modifications in coloration would result in modifications in brightness and vice versa. It was to common these modifications out over time that the NTSC specified that the relative section reversal of the 2 alerts might happen on successive fields. The result’s extra pleasing coloration transitions, however the section shift makes stationary figures seem to jitter. The jitter is especially apparent on skinny vertical traces, like these in alphanumeric characters. However when the Commodore 64 was conceived, it was to be primarily a recreation machine, not a pc.

Working a 5-micrometer-technology chip at an 8-MHz clock charge brought about it to dissipate a substantial amount of energy—almost 1.5 watts. Not solely did the chip run quick, however to forestall the colours from washing out, as they’d within the VIC-20, “we went to 12 volt to drive the heck out of the colour alerts,” recalled Winterble. “We knew we might have a warmth drawback.”

At this level Winterble made one other design repair—welding a small metallic tab onto the within of the lid of the shielding enclosure across the video chip. When the pc was assembled, the tab pressed in opposition to the highest of the chip bundle, forming a heat-conducting path and turning the shielding right into a warmth sink.

Some modifications which may have improved the machine didn’t get made within the rush to manufacturing. For instance, Yannes mentioned, the wires for the sound output on the printed-circuit board run alongside the wires for the video sign. Because of this, the sound output picks up an annoying 15,750 -Hz whine. Rerouting the circuit would have taken time, “and we had a board that labored,” he defined. “At that time, in the event you had one thing that labored, you didn’t change it.” A circuit-board revision since then has rerouted these traces, Commodore mentioned.

However the designers did the truth is change some issues that labored—together with one revision that degraded the machine’s efficiency.

However the designers did the truth is change some issues that labored—together with one revision that degraded the machine’s efficiency. The unique design specified a high-quality radio-frequency modulator to transmit the sign to a tv set, however a less expensive modulator was substituted. “It was $6.25 to $6.50 for a great one, and we ended up spending about $3,” Charpentier mentioned.

Winterble has a unique view of the $3 modulator: “The 50-cent modulator we have been utilizing on the VIC-20 wasn’t adequate,” he mentioned, “so we went to a costlier one.”

Digital design wasn’t the one tough space because the Commodore 64 went from prototype improvement into manufacturing—the logistics posed a posh drawback. The C-64 was designed in Norristown, Pa., at MOS. The VIC-20 meeting line, which was to start making C-64s, was in Santa Clara, Calif. Because the C-64 went into manufacturing, Commodore was additionally opening a brand new meeting line in West Chester, Pa. There have been extra VIC-20 meeting services in Japan, the place the disk drive for the C-64 was to be manufactured. And the C-64 circuit boards have been being made in Hong Kong.

“It was quite a lot of enjoyable,” mentioned Ziembicki. “The design individuals would decide an English screw. The manufacturing finish would decide metric. However they went with what they’d. Commodore manufacturing was excellent at making issues match whether or not they have been meant to or not. Their constitution was ‘Ship ‘em’”

“It takes a really powerful particular person,” defined Charpentier, “to say ‘I’m not delivery these as a result of they’re inferior to they might be’—particularly when individuals are clamoring to purchase them.”

​Modifications proceed throughout manufacturing

The beginning of manufacturing of the Commodore 64 within the spring of 1982 didn’t sign an finish to the controversy. “The secret’s to have the ability to resolve your issues while you’re operating,” mentioned Ziembicki.

One of many first battles, recalled Charpentier, was over the format of the printed-circuit board. Commodore’s meeting plant in america used automated component-insertion gear, however its Japanese facility didn’t, and the 2 meeting strategies required totally different element spacing. Ultimately, the board for the C-64 was laid out for automated insertion, and manufacturing was moved to a brand new plant in Hong Kong that had the automated instruments.

Issues additionally plagued a variety of the parts—switches, for instance. “You decide a swap that’s listed as a shopper swap,” mentioned Ziembicki. “You design it in. You name the producer and get an estimate that sounds affordable. Then California [the production division] needs 50,000 every week, however the producer says, ‘We are able to’t make that. It’s a shopper swap, however we’re not geared for shopper portions.’ At that time, you’re hung up.”

Since Commodore had simply moved its engineering workers from California to Pennsylvania, communication between the design engineers and the manufacturing services was not excellent, Ziembicki defined. “It obtained to the purpose the place you couldn’t cease working even in the event you didn’t get an answer—you’d simply proceed with the parts that you just thought the manufacturing finish might get.”

And outdoors suppliers weren’t all the time dependable. “One offered an influence provide for engineering approval,” Ziembicki recalled. “It obtained accepted, after which the provider modified the design and didn’t inform anyone.”

Charpentier mentioned that his relations with the manufacturing group have been pretty agreeable. Winterble’s dealings with them weren’t almost as cordial, however he discovered this acceptable. “I personally needed to play the heavy on quite a lot of stuff,” he mentioned. “Then Al would go in and do some good. That approach eased quite a lot of rigidity—it was a option to get issues executed.”

Essentially the most infamous drawback was “sparkle,” a defect that brought about small spots of sunshine to seem on the show display screen. The issue was solved earlier than Charpentier left the corporate in September 1982, however stories of the defect continued effectively into the Christmas season, with press stories citing it for instance of Commodore’s poor high quality management. Canny shoppers used it as an excuse to return completely good Commodore 64s whereas they have been below 90-day guarantee. Because the value of the machine had dropped $200 within the two months following its introduction, this ruse enabled homeowners to acquire a refund of the acquisition value and purchase one other C-64 on the decrease determine.

Sparkle was extensively attributed to bugs within the video chip that was the center of the system, however the truth is it was brought on by a ROM chip of which 3 million have been in service with no issues in different techniques, together with the hit arcade online game Asteroids. Commodore engineers themselves first seemed for the issue within the video chip. It took them three weeks to identify the ROM chip because the supply of the defect, Charpentier mentioned. “The issue was a random occasion—it didn’t occur on a regular basis. We thought the video chip was for some purpose seeing the fallacious information. We didn’t even suspect it might be the ROM. Lastly we put the logic analyzer on it and tracked it down.” The ROM, which Charpentier and his group had designed years earlier, had a particular pre-charging circuit to make it run sooner, however the circuit made it delicate to spurious alerts. The video circuitry and the 6510 microprocessor alternated in controlling the system bus, and when management handed kind one to the opposite, voltage spikes have been typically generated.

“It simply occurred that we hit the precise timing,” Charpentier mentioned. “If the spike had been a number of nanoseconds shorter or longer, it wouldn’t have been an issue. The spike was simply extensive sufficient that the ROM noticed it as a legitimate deal with. It will ignore the subsequent deal with request and provides the video chip fallacious information.” Because the ROM contained the C-64 character set, the display screen show can be suffering from random slices of characters.

In keeping with Nelson of Epyx, “This confetti interference-looking stuff on the display screen, glowingly known as sparkle, has a particularly un-nice property: it causes {hardware} collisions—the sprites consider it actually exists.” Because the sparkle was brought on by inappropriate information fed to the video chip, it triggered the circuitry chargeable for checking whether or not the movable show objects—sprites—have been overlaying background objects on the display screen. So software program that trusted collision sensing to manage the motion of objects on the display screen would go berserk when confronted by sparkle.

The bug within the ROM was corrected, though Commodore needed to depend on outdoors suppliers for some time because it ramped up its new manufacturing line. Solely the primary few hundred thousand items shipped had the defect. However, Nelson noticed, “it doesn’t matter to programmers that it was mounted. Our software program has to work in each machine on the market.” One of the best resolution for programmers, he defined, is to repeat the contents of the ROM into RAM, which is dependable. However this wastes 2 kilobytes of RAM.

​“A screw-up in my timing”

Along with the issue with the ROM, “I made a logic error,” Charpentier recalled. The error, which was corrected typically after Charpentier left Commodore, brought about the early C-64s to generate the fallacious variety of clock cycles on every horizontal video line. “It was off by one,” he mentioned. “As a substitute of 65 clock cycles per line, I had 64.”

Because of this, the 180-degree section shift between the black-and-white and coloration data, which might have eradicated color-transition issues, didn’t happen. Relying on their coloration and the colour of the background, the sides of some objects on the display screen would seem barely out of line. This was corrected roughly 5 months into manufacturing.

However main edges are nonetheless an issue with the C-64. The circuitry that shows both sprite data or background data at any level on the display screen is typically gradual to reply and overlays the sprite on the background data solely after it has missed a number of pixels.

The C-64 designers weren’t the one ones revising their machine; even some assembly-line employees obtained into the act.

The C-64 designers weren’t the one ones revising their machine; even some assembly-line employees obtained into the act. Since testing coloration high quality routinely is nearly not possible, assembly-line employees have been instructed to show a potentiometer that controls the colour and black-and-white alerts till they noticed coloration. As Charpentier recalled, the employees quickly found that in the event that they turned the potentiometer so far as doable, it resulted in saturated coloration—nevertheless it additionally worn out the black-and-white sign. A number of thousand computer systems had been shipped earlier than the assembly-line employees’ “revision” was seen; by then, some reviewers have been lambasting the C-64 for its “garish” colours.

​High quality nonetheless missing

Although these modifications have been made within the C-64 since its introductions, designers who write business software program for the machine want to see a number of extra. One such change can be satisfactory high quality management. “They don’t take a look at,” mentioned Nelson of Epyx. “I’ve opened up brand-new Commodores and located traces minimize. They clearly use an influence screwdriver to assemble the C-64, typically miss the screw, and chop the traces. How, may you surprise, might which have handed closing inspection? Effectively, these traces are hooked as much as the disk-drive connectors, which they clearly don’t take a look at.”

In hindsight, Charpentier known as considered one of Commodore’s errors “not coming a bit nearer to high quality.”

One grievance voiced by designers of add-on {hardware} for the C-64 is that its minimalist design ends in undesirable interactions between components of the {hardware} and software program. For instance, the circuitry used to manage the joystick and the game-paddle port is borrowed as soon as each 1/60 second to scan the keyboard for keys which were pressed. If the joystick switches are closed, the keyboard-scanning software program will report {that a} key has been pressed. Gadgets that connect to the joystick ports could cause unpredictable responses—an issue that may not happen if separate {hardware} had been used for the 2 capabilities.

One other flaw is the pc’s crude inside software program. The system comes up in Fundamental when it’s turned on. This can be a leftover from the times of the primary Pet laptop produced by Commodore, which had no disk-operating system, since there have been no disk drives available then. “An honest disk-operating system wasn’t developed till Pet Fundamental 4.0,” Charpentier mentioned. The C-64 doesn’t use this superior model of Fundamental as a result of “it could have required extra ROM than we might put in.” As a substitute, the machine makes use of a much more primitive model of Fundamental, borrowed from the VIC-20.

“Software program wasn’t tangible—you couldn’t maintain it, really feel it, or contact it—so it wasn’t price spending cash for.”

Essentially the most evident omissions from the Commodore 64’s Fundamental are instructions to manage the sound and graphics chips. “There was by no means any intention that the system would have built-in software program to manage the graphics or the sound,” mentioned Yannes. “That was an apparent a part of the Commodore philosophy; you don’t waste cash on issues that make the product costlier and that almost all of consumers aren’t going to make use of.”

“Commodore has all the time paid lip service to software program,” Charpentier mentioned. “They do sufficient to get by after which depend on outdoors sources to fill the hole. Commodore was an extension of Jack Tramiel, and to him software program wasn’t tangible—you couldn’t maintain it, really feel it, or contact it—so it wasn’t price spending cash for.”

The C-64 designers had plans of their very own for modifications which haven’t but been carried out. They used the VIC-20 case to shortcut improvement, however they did have a brand new case designed that they meant to substitute in eight to 10 months. “It was thinner in entrance and had extra of a wedge form to it,” mentioned Charpentier. “I all the time thought the VIC-20 case seemed clunky.” A couple of new options have been additionally to be added to the machine.

The truth that these modifications haven’t been made has probably not affected the success of the C-64, asserted Brian Dougherty, president of the Berkeley Softworks of Berkeley, Calif. “This machine has the very best graphics-display functionality of something that has but been executed for a TV display screen,” he mentioned. “It got here sloe to being an superior system.”

​The albatross of the C-64: its disk drive

The one main flaw of the C-64 shouldn’t be the machine itself, however in its disk drive. With a fairly quick disk drive and an satisfactory disk-operating system (DOS), the C-64 might compete within the enterprise market with the Apple and maybe with different enterprise computer systems. With the current disk drive, although, it’s hard-pressed to lose its picture as a toy.

“Enterprise-oriented software program doesn’t look nearly as good because it ought to on the C-64,” mentioned Dougherty, “not as a result of the bottom system isn’t adequate however as a result of the disk-drive entry is just too gradual; any enterprise software requires quite a lot of disk entry.” And because the DOS is so weak and lacks options reminiscent of the automated creating and sustaining of directories and conserving observe of recordsdata, “it’s much more tough to develop enterprise software program” for the C-64, he added. “Any individual like Lotus [Development Corp., manufacturer of a popular integrated business-software package] is dealing with much more issue than they did creating software program for the IBM PC, as a result of the PC has an operating-system construction that simply doesn’t exist for this product.

“The fundamental input-output system in ROM is finished pretty cleanly, in accordance with operating-system ideas. All of the routines that should be there are there, however there must also be a facility for routinely studying the primary observe of the disk and booting a extra subtle working system into reminiscence.”

The disk drive does the truth is have a facility for routinely studying the primary observe of a disk, in accordance with Nelson of Epyx, however as a result of it isn’t documented, it isn’t extensively used.

How did the Commodore engineers botch up the disk drive?

“The disk drive? What a gory story!”

“The disk drive? What a gory story!” Charpentier mentioned. “That needed to do with the one advertising enter we did settle for. Advertising and marketing mentioned the C-64 needed to be appropriate with the VIC-20.”

The disk drive on the VIC-20, Charpentier defined, was a direct descendant of the drive on the Commodore Pet laptop. “We had a parallel IEEE-488 bus for the Pet disk drive; and we used an odd format within the early days so as to pack information: on the outer tracks, the disk strikes sooner than on the interior tracks, so the info charge modifications so as to pack extra information on the market. It was a pleasant thought, nevertheless it was clumsy, in that you just’re incompatible with everybody else. That’s the nut this all began with.”

The VIC-20 disk drive was designed in Japan, and the bus was modified from parallel to serial to economize. The drive could be very gradual as a result of the serial-interface portion of the interface controller (the 6522) used on the VIC-20 doesn’t work. Because of this, the 6502 processor sends out one bit at a time below direct software program management, fairly than sending a byte to the peripheral controller and letting it maintain clocks, information, and hand shaking.

“We mounted the serial-shift register for the 6526 [the interface controller used on the C-64 to replace the 6522] however we couldn’t use it, as a result of the disk drive needed to be appropriate,” Charpentier continued. “And, as a result of the processor within the C-64is turned off for 40 microseconds each 512 microseconds, it stored lacking the interrupt alerts that management the disk interface. The answer: gradual the drive down even additional.”

Velocity was the one issue that would have been modified with out incurring the price of radical modifications within the disk drive; if the C-64 designers had been in a position to forgo VIC-20 compatibility, they may have executed significantly better. And ultimately, in fact, the C-64 was not appropriate with the disk drive of the IC-20 anyway.

“All of it stemmed from the 6522 serial interface not working,” Charpentier concluded.

Different producers try to resolve the disk-drive drawback of the C-64. Some are promoting their very own disk drives to be used with the C-64, however they’ve discovered it tough to interrupt right into a market that Commodore controls. Others are promoting packages that may be loaded into RAM to hurry up disk-transfer charges, however this selection applies solely to make use of of the C-64 for programming in Fundamental; prepackaged software program loaded into the system knocks the packages out of RAM. Epyx has launched a ROM-based program to hurry disk switch fivefold. In keeping with Nelson, this system will work with any disk-based software program. “That’s doable,” mentioned Charpentier. “The C-64 disk drive has its personal microprocessor and reminiscence, and you’ll ship data to it to vary the working system and to hurry up the serial-bus protocol.”

The usual software program for the C-64 disk drive can learn a 256-byte sector each 2.5 revolutions of the disk, or 512 byes per second. Programming tips utilized by Epyx have yielded switch charges of as much as 2.5 kilobytes per second. (Amongst different gradual disk drives, Atari’s 810 transfers 1000 bytes per second, and the Apple II disk drive runs at a most of 15,000 bytes per second.)

Intelligent design shaves pennies

The Commodore staff had labored exhausting to make sure a low preliminary manufacturing price for the C-64. Vertical integration helped hold components prices down, and Winterble vetoed concepts for added options. The designers themselves believed in counting pennies; Charpentier mentioned he had realized rather a lot” from Jack Tramiel, who was “an actual stickler for price. We agonized over each transistor.”

With a manufacturing price of $135 and a retail value of $595 at its introduction, the Commodore 64 would have a retail markup comfortably above the trade normal of 1 to a few (maybe one to 2 when volumes climb). However Commodore has continued to search out methods to scale back each the retail value, now $149, and the manufacturing price, believed to be between $35 and $50 in the present day.

Commodore wouldn’t verify this price determine. Dougherty of the Berkeley Softworks estimated the prices of C-64 components, base don his expertise at Mattel and Imagic.

  • Three ROMS at $1 every.
  • Eight dynamic Rams at $1.85 every.
  • SID (sound) chip and VIC (graphics) chip at $4 every.
  • RF modulator bundle, $3
  • 6510 microprocessor, $1 to $2
  • A handful of TTL, buffers, energy regulators, and capacitors for a complete of $5
  • Keyboard, lower than $10
  • PC board, $1 to $2
  • Plastic case, $1 to $2
  • Energy provide and miscellaneous connectors, $5 to $10
  • Packaging and handbook, $1 to $2

In additional cost-cutting strikes, Commodore has changed the TTL with cheaper customized chips and has discovered methods to extend yields on the sound and graphics chips.

Not all cost-cutting steps have been with out detrimental impact on the system. The 6567 video chip was initially packaged in ceramic, despite the fact that plastic is less expensive. “We tried every kind of issues,“ Charpentier mentioned, “copper-lead frames, metallic inserts within the bundle, and an ungodly variety of different issues to get a plastic bundle, as a result of a ceramic bundle could be very costly. However we couldn’t discover a bundle that ran cool sufficient. Earlier than I left Commodore, I listed some concepts to scale back the ability, however half of the chip was nonetheless operating at an 8-MHzclip. And not using a main redesign, you can not get the ability out.”

The design staff was autonomous—they did their very own market analysis, developed their very own specs, and took their child proper up by means of manufacturing.

The chip is now encased in plastic. Commodore engineers mentioned that along with redesigning the chip, they’ve developed a plastic bundle that may dissipate warmth in addition to ceramic.

Because the change to plastic packaging, a variety of new issues with the C-64 have been reported—issues which can be machine-specific or temperature-dependent. One failing that’s extensively identified all through the software program trade is an inclination for the chip to lock up when a program switches graphics modes—from displaying a bit map to displaying characters [see sidebar, “A Rich Collection of Graphics Modes”]. “A recreation we have been producing began to fail on the manufacturing line,” mentioned Nelson of Epyx. “Then we’d take a look at [defective disks] once more they usually’d work. It trusted which machine we put them on and what the temperature was.” Charpentier speculated that some circuit traces had been left floating within the authentic design; poor processing and excessive working temperatures would stress chips to the failure level.

One other drawback that has begun to emerge in some C-64s is defective horizontal scrolling of bit-mapped screens. In a latest evaluate of the Summer time Video games, an Epyx sports activities recreation for the C-64, the San Jose, Calif., Mercury Information criticized the “flashbulb impact” noticeable throughout the swimming occasion. That, in accordance with Nelson, shouldn’t be an “impact”—the C-64 utilized by the Mercury Information reviewer merely doesn’t do horizontal scrolling correctly.

The liberty ended

Though the machine has its flaws, the designers of the Commodore 64 consider they got here up with many vital advances due to the liberty they loved throughout the early levels of the challenge. The design staff was autonomous—they did their very own market analysis, developed their very own specs, and took their child proper up by means of manufacturing. However as quickly because the manufacturing bugs have been labored out and Commodore knew it had a winner, the company paperwork, which till then had been on the West Coast coping with the VIC-20 and the Pet laptop, moved in.

“At that time, many advertising teams have been coming in to ‘assist’ us,” Winterble recalled. “The following product definition was going to be thought up by one group, and one other group was to be chargeable for getting issues into manufacturing, and Al’s group would do R&D on chips solely.”

“In case you let advertising get entangled with product definition, you’ll by no means get it executed rapidly,” Yannes mentioned. “And also you squander the power to make one thing distinctive, as a result of advertising all the time needs a product appropriate with one thing else.”

Charpentier summed up their frustration: “While you get many individuals concerned in a challenge, all you find yourself doing is justifying your self. I knew the Commodore 64 was technically nearly as good and as low-cost as any product that might be made on the time, however now I needed to take heed to advertising individuals saying, ‘It gained’t promote as a result of it doesn’t have this, it may possibly’t do this.’

“The liberty that allowed us to do the C-64 challenge will most likely by no means exist once more in that surroundings.”

​Postscript (as of March 1985)

Of the unique Commodore 64 design staff, solely Robert Russell stays at Commodore; he’s presently a design supervisor. The remainder of the staff—Albert Charpentier, Robert Yannes, and Charles Winterble, together with David Ziembicki and Bruce Crocket, who helped debug the challenge and convey it into manufacturing—left Commodore within the spring of 1983 and shaped the corporate Peripheral Visions. Their plan was to design one other laptop. To acquire working capital, they took on a contract from Atari—to design a keyboard for the Video Pc System, which was previewed however then, because the videogame market crashed, by no means launched. Peripheral Visions was sued by Commodore, which mentioned the VCS keyboard was a challenge that belonged to Commodore. At this writing, the go well with had not been resolved.

Peripheral Visions has been renamed Ensoniq and can quickly launch its first product, a music synthesizer. Albert Charpentier is presently vp of engineering at Ensoniq, Bob Yannes is senior designer, and David Ziembicki is supervisor of manufacturing management. Charles Winterble left Peripheral Visions and is now group vp of electronics at Coleco Industries Inc. of West Hartford, Conn. And Jack Tramiel is presently chief government officer of Atari Corp., the corporate that was Commodore’s chief competitor within the home-computer market earlier than dropping almost a billion {dollars} in competing in opposition to the C-64.

To probe additional

Pc bookstores carry a big selection of books on the C-64. Amongst these advisable are
What’s actually contained in the Commodore 64, by Bilton Bathurst, printed by DataCap of Feneur, Belgium, and The Anatomy of the 1541 disk drive, by Lothar Englisch and Norbert Szczepanowski, printed by Abacus Software program of Grand Rapids, Mich. Pc magazines reminiscent of Artistic Computing and Compute! evaluate software program and publish packages that run on the C-64. The Commodore 64 itself could be discovered at most giant retailers.

How Programmers Exploited the C-64 {Hardware} (Slideshow)


A Synthesizer on a Chip

“I’d labored with synthesizers, and I needed a chip that was a music synthesizer,” mentioned Robert Yannes, the sound-chip designer and techniques architect for the Commodore 64. He started engaged on the chip within the spring of 1981, assisted by two draftsmen and one CAD operator. “No person else had a good suggestion of what we have been doing,” he mentioned. “Past primary analysis, which I’d been doing since highschool, the precise design took solely about 4 or 5 months.”

The most important variations between his chip and the everyday videogame sound chips, Yannes defined, have been its extra exact frequency management and its unbiased envelope for shaping the depth of a sound. “With many of the sound results in video games, there’s both full quantity or no quantity in any respect. That actually makes music not possible. There’s no option to simulate the sound of any instrument even vaguely with that sort of envelope, besides possibly an organ.”

Though it’s theoretically doable to make use of the amount controls on different sound chips to form the envelope of a sound, only a few programmers had ever tackled such a posh process. To make sound shaping simple, Yannes put the envelope controls in {hardware}: one register for every voice to find out how rapidly a sound builds up; two to find out the extent at which the word is sustained and how briskly it reaches that stage; and one to find out how briskly the word dies away. “It took a very long time for individuals to grasp this,” he concluded.

Yannes additionally put a lookup desk within the {hardware} to transform information from musical notes to the equal frequencies, however that required extreme silicon. “I took that out,” mentioned Charles Winterble, who was worldwide-engineering director at Commodore throughout the C-64 design.

The exact capabilities of the sound chip aren’t clear even in the present day, largely due to incorrect specs having been written when the chip was first designed. “The spec sheet obtained distributed and copied and rewritten by varied individuals till it made virtually no sense anymore,” mentioned Yannes. An instance of the defective documentation is the declare that the chip can logically AND a number of waveforms. The chip can produce both a triangular wave, a sawtooth, or a sq. wave, relying on which bit is about in considered one of its management registers. “There is no such thing as a interlock to make it possible for if one bit is on, the others are off,” Yannes mentioned. “That might have taken an excessive amount of silicon.” So if multiple waveform is elected, the inner notes of the output multiplexer are discharged, and what emerges is the minimal of amplitudes.

One other error within the spec sheet considerations the on-chip filters. “The filter was the very last thing that was labored on,” Yannes acknowledged. “I ran out of time. The pc simulation mentioned, ‘This won’t work very effectively’—and it didn’t.” The filter could have been mediocre, however the equations describing the way it labored have been simply plain fallacious, Yannes recollects. “They didn’t cling collectively. Nobody gave me an opportunity to right them.”

Confronted by these incorrect equations, most software program designers use solely the sound chip.

A number of the Japanese programmers who wrote early recreation software program for the C-64 took a unique method, Yannes famous: “They wrote it in accordance with the spec. It didn’t matter to them whether or not one thing labored or not. Because of this, packages made sound results you couldn’t hear.”

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