by Ian Matthews of Commodore.ca July 11 2003 – Revised Feb 27 2025
On this page:
In the summer of 1984 Commodore decided that they needed a replacement for the amazingly successful C64. More accurately, they decided that the TED / 116 / Plus/4 / 264 Series was a failure as a replacement for the C64.
Customer reaction to Commodores failure to provide native CP/M support in the C64 and (much worse) their failure to provide C64 compatibility in the Plus/4 / 264 Series taught Commodore engineers some hard lessons. Commodore’s founder and visionary, Jack Tramiel, had quit months earlier and the new management team wanted to just forget the Plus/4 / 264 Series fiasco. The engineers knew they needed a new product and that product had better be compatible with the best selling computer in the world, the C64.
Bil Herd got the top job as 128 lead Engineer because of his vocal criticism of the new management teams lack of vision:
“No one dreamed that C64 compatibility was possible so, no one thought along those lines. I had decided to make the next machine compatible with something instead of yet another incompatible CBM machine. (I won’t go into the “yes Virginia there is Compatibility” memo that I wrote that had the lawyers many years later still chuckling, suffice it to say I made some fairly brash statements regarding my opinion of product strategy). Consequently, I was allowed/forced to put my money where my mouth was and I took over the C128 project.”
“I looked at the existing schematics once and then started with a new design based on C64’ness. The manager of the chip group approached me and said they had a color version of the 6845 if I was interested and it would definitely be done in time having been worked on already for a year and a half… And so the story begins.”
Commodore needed its next computer to be a serious upgrade from the C64 if it was to successfully battle its arch nemesis; it needed to keep Jack Tramiel’s, Atari, from besting them with features in the their rumored new “ST” line.
In 1982, Commodore released the worlds first multi-processor personal computer, called SuperPET, but it was $2800 ($8600 in 2023 dollars) and targeted at the education / scientific markets. The Commodore 128 was to be the worlds first mass market multi-processor computer. It would also have two video subsystems, one of which would allow it to connect to a TV.
A reviewer from Your Computer magazine wrote
“The dowdy shoebox image of the Commodore 64 has been replaced by a slim line beige console that any style-conscious businessman should be pleased to have on his desk. A full size typewriter style keyboard has 92 keys, that travel and locate well.”
The 128’s 80 column display mode would produce 640×200 which was better than the CGA mode that IBM PC’s could produce even in the early 1990’s! This new an powerful machine would act as three completely separate computers in one:
| Commodore 128 Mode | 2Mhz Speed (8502 CPU), 128K Memory, very nice 80×25 RGB display, advanced Basic 7.0 |
| Commodore 64 Mode | 1Mhz Speed (6510 emulation in the 8502 CPU), 99.8% compatible with C64 hardware and software, accessed by booting the machine while holding down the Commodore key or typing GO 64 |
| Commodore CP/M Mode | 1-4Mhz Speed (Zilog Z-80 CPU), 100% compatible with the huge volume of CP/M business applications such as Turbo Pascal and WordStar (an excellent program I used personally for years on a Sanyo MBC555 !) Note that the Z-80 processor was originally spec’d by Commodore management to be the same external expansion cartridge used on the C64. However, to resolve several other engineering problems, Bil Herd designed the Z-80 into the main board. This mode required CP/M software disks to be loaded on boot up. |
All this would sell for an initial price of just $300 ($925 in 2023 dollars); half of the Commodore 64 price when it was introduced two years earlier.
| MOS 8502 | CPU – Yet another derivative of the 6500 series |
| Zilog Z-80 | Improved version of Intel 8080 CPU designed by the same Intel engineer |
| MOS 8563 | CRCT / VDC – Video Display Chip 80 column x 25 rows 640×200 (128 mode only) |
| MOS 8564/6 | VIC – Video Interface Chip (NTSC / PAL) – used in 40 column x 25 row |
| MOS 8721 | FLPA |
| MOS 8722 | MMU – Memory Management Unit |
| MOS 6581 | SID – Sound Interface Chip |
| MOS 6526 | CIA – Complex Interface Adaptors (2 of them!) |
This technically complex machine would present serious engineering and marketing challenges to any company.
Bil Herd recalls:
“It was sometime in September (1984) when we got 8563 (new 40/80 column color video chip) Silicon, good enough to stick in a system. …One concern we had was it occasionally blew up…. big time…. turn over die and then smell bad….. But then all of the C128 prototypes did that on a semi regular basis as there wasn’t really any custom silicon yet, just big circuit boards plugged in where custom chips would later go… but you can’t wait for a system to be completed before starting software development. When this problem still existed on Rev 4 we got concerned. It was at this time that the single most scariest statement came out of the IC Design section in charge of the ’63. This statement amounted to ‘you’ll always have some chance statistically that any read or write cycle will fail due to (synchronicity)’ “.
“Synchronicity problems occur when two devices run off of two separate clocks, the VIC chip hence the rest of the system, runs off of a 14.318Mhz crystal and the 8563 runs off of a 16Mhz Oscillator. Now picture walking towards a revolving door with your arms full of packages and not looking up before launching yourself into the doorway. You may get through unscathed if your timing was accidentally just right, or you may fumble through losing some packages (synonymous to losing Data) in the process or if things REALLY foul up some of the packages may make it through and you’re left stranded on the other side of the door (synonymous to a completely blown write cycle). What I didn’t realize that he meant was that since there’s always a chance for a bad cycle to slip through, he didn’t take even the most rudimentary protection against bad synchronizing. …As it turns out the 8563 instead of failing every 3 years or so (VERY livable by Commodore standards) it failed about 3 times a second.”
In addition the yield on these video chips was about .001%. Commodore’s chip division MOS Technologies could only get three or four working chips the per run. “A run is a half-Lot at MOS and costs between $40,000 and $120,000 ($120K to $370K in 2023 dollars) to run. Pretty expensive couple of chips.”
As if these problems were not enough, the power supply needed to be adjusted for each chip or they would literally burn up.
“No single custom chip was working completely as we went into December (1984) with the possible exception of the 8510 CPU… At this point all I did have to lose was a HUGE jar of bad 8563’s. (One night a sign in my handwriting “appeared” on this jar asking “Guess how many working 8563’s there are in the jar and win a prize.” Of course if the number you guessed was a positive real number you were wrong.)”
With only five or six weeks to go until the January Consumer Electronics Show in Vegas “…finger pointing was in High swing, (the systems guys should have said they wanted WORKING silicon) with one department pitted against the other, which was sad because the other hardworking chip designers had performed small miracles in getting their stuff done on time… …Managers started getting that look rabbits get in the headlights of onrushing Mack trucks, some started drinking, some reading poetry aloud and the worst were commonly seen doing both. Our favorite behavior was where they hid in their offices. It was rumored that the potted plant in the lobby was in line for one of the key middle management positions.” Unbelievably, in this time of crisis, both MOS chip designers went on Christmas vacation and “…a sprinkler head busted and rained all over computer equipment stored in the hallway. Engineering gathered as a whole and watched on as a $100,000 worth of equipment became waterlogged…. I can honestly say that it didn’t seriously occur to me that we wouldn’t be ready for CES… here were just too many problems to stop and think what if.”
“Von Ertwine was developing CP/M at home (consultant). Von had wisely chosen not to try to follow all of the current Revs of the 8563, instead he latched onto a somewhat working Rev4 and kept if for software development. Later we would find out that Von, to make the 8563 work properly, was taking the little metal cup that came with his hot air popcorn popper (it was a buttercup to be exact) and would put an Ice cube in it and set it on the 8563. He got about 1/2 hour of operation per cube. On our side there was talk of rigging cans of cold spray with foot switches for the CES show.”
“A true miracle and was accompanied by the sound of Hell freezing over, the rabbit getting the Trix, and several instances of cats and dogs sleeping together. This was the first time that making CES became a near possibility. We laughed, we cried, we got drunk.”
“We averaged 1-3 of these crises a day the last two weeks before CES. Several of us suffered withdrawal symptoms if the pressure laxed for even a few minutes. The contracted security guards accidentally started locking the door to one of the development labs during this time. A hole accidentally appeared in the wall allowing you to reach through and unlock it. They continued to lock it anyways even though the gaping hole stood silent witness to the ineffectiveness of trying to lock us out of our own lab during a critical design phase. We admired this singleness of purpose and considered changing professions.”
“We finished getting ready for CES about 2:00am in the morning of the day we were to leave at 6:00am.”
“Advertisements in the Las Vegas airport> and again on a billboard en-route from the airport inform us that the C128 has craftily been designed to be expandable to 512K. Now it had been designed to be expandable originally and had been re-specified by management so as to not be expandable in case next year’s computer needed the expandability as the “New” reason to buy a Commodore computer. That’s like not putting brakes on this years model of car so that next year you can tote the new model as reducing those annoying head-on crashes.”
You can see in the advert to the right that a massive 512K expansion was eventually made, but not by Commodore. This was from Berkely Softworks in 1990!
“Upon arriving at the hotel we find that out hotel reservations have been canceled by someone who fits the description of an Atari employee. Three things occured in rapid succession. First I find the nearest person owning a credit card and briskly escort her to the desk were I rented a room for all available days, second, a phone call is placed to another nearby hotel canceling the room reservations for Jack Tramiel and company, third, several of those C64’s with built in monitors (C64DX’s??? man it’s been too long) are brought out and left laying around the hotel shift supervisors path accompanied by statements such as “My my, who left this nifty computer laying here… I’d bet they wouldn’t miss it too much”. “The next day we meet up with the guy who developed CPM (Von) for the C128. As I mentioned earlier, someone forgot to tell him about the silly little ramifications of an 8563 bug. His ‘puter didn’t do it as he had stopped upgrading 8563s on his development machine somewhere around Rev 4 and the problem appeared somewhere around Rev 6. As Von didn’t carry all the machinery to do a CP/M rebuild to fix the bug in software, it looked like CP/M might not be show-able. One third of the booth’s design and advertising was based on showing CP/M. In TRUE Animal fashion Von sat down with a disk editor and found every occurrence of bad writes to the 8563 and hand patched them. Bear in mind that CP/M is stored with the bytes backwards in sectors that are stored themselves in reverse order. Also bear in mind that he could neither increase or decrease the number of instructions, he could only exchange them for different ones. Did I mention hand calculating the new checksums for the sectors? All this with a Disk Editor. I was impressed.”
“Everything else went pretty smooth, every (power) supply was adjusted at the last moment for best performance for that particular demo. …On the average, 2 almost working 8563’s would appear each day, hand carried by people coming to Vegas. Another crisis, no problem, this was getting too easy.”
Commodore did not produce many peripherals designed exclusively for the 128 line because they did not have to. They relied primarily on existing C64 devices like the 1541 floppy drive. An exception was the Commodore 1902 monitor for $400 (which $1200 in 2023 dollars and was $100 more than the price of a new C128!) which was required to use the new 128’s advanced 80 column mode. The C1750 massive 512K RAM Expander was another new product. The most anticipated new peripheral was the 1571 double sided floppy drive which, at 360K, provided more than double the capacity of the 1541. Much more importantly it was a whopping 7 to 10 times faster!
Many Bulletin Board Systems (BBS’s – pre-internet for those of you who were born after 1980) also jumped on the C128 Mode bandwagon. There are a number of historians who site Commodore as the unsung development partner of the Internet. While it is certainly true that the US military and several universities developed ARPANET, its transition into the internet would not have been so rapid had online communities not been created with extensive use of Commodore hardware: the amazingly inexpensive VIC Modem (and its decedents the 1600, 1650, 1670 and 1680) combined with powerful C128 Mode functionality allowed thousands of BBS’ to spring up from nothing. The 128 produced:
all of which were required to develop and commercialize the Internet.
In an effort to extend the life of this powerful multi-talented machine, Commodore introduced a slight derivative of the 128 called the Commodore 128D in 1987. The idea was to make a cleaner, smaller foot print for the 128 so that it might appeal to the small business segment dominated by IBM at the time. Commodore 128D models looked allot like Apple Mac computers of the late 1990’s. They came in a square desktop box, featuring an integrated front loading Commodore 1571 5.25″ high capacity floppy disk drive, and a separate keyboard. A monitor could sit nicely on top of this chassis, again reducing desk space requirements and clutter. The price of this system, just $500 ($1500 in 2023 dollars), a third the price of an IBM PC.
In a cost saving effort, D’s were manufactured with less expensive “upgrade” versions of the SID (sound) chip, called the 8580 SID and were sometimes referred to a 128DCR’s (Cost Reduced).
The first European 128D’s chassis were made of plastic. They came with a keyboard dock and carry handle! The North American model came in standard beige steel chassis’ without the carry handle or keyboard dock.
On an amusing note, I have often been asked questions from non-Commodore collectors about a super-rare prototype called a Commodore 1280. Of course this is simply a misreading of the Commodore 128D name.
Today (in 2003), 128D models are highly sought after by collectors and enthusiasts, usually garnering more than triple what a standard 128 sells for.
Bil Herd explains “The names of the people who worked on the PCB layout can be found on the bottom of every PCB.”
| Bil Herd | Original design and hardware team leader. |
| Dave Haynie | Integration, timing analysis, and all those dirty jobs involving computer analysis which was something totally new for CBM. |
| Frank Palaia | One of three people in the world who honestly knows how to make a Z80 and a 6502 live peacefully with each other in a synchronous, dual video controlled, time sliced, DRAM based system. |
| Fred Bowen | Kernal and all system like things. Dangerous when cornered. Has been known to brandish common sense when trapped. |
| Terry Ryan | Brought structure to Basic and got in trouble for it. Threatened with the loss of his job if he ever did anything that made as much sense again. Has been know to use cynicism in ways that violate most Nuclear Ban Treaties. |
| Von Ertwine | CPM. Sacrificed his family’s popcorn maker in the search of a better machine. |
| Dave DiOrio | VIC chip mods and IC team leader. Ruined the theory that most chip designers were from Pluto. |
| Victor | MMU integration. Caused much dissention by being one of the nicest guys you’d ever meet. |
| Greg Berlin | 1571 Disk Drive design. Originator of Berlin-Speak. I think of Greg every night. He separated my shoulder in a friendly brawl in a bar parking lot and I still cant sleep on that side. |
| Dave Siracusa | 1571 Software. Aka “The Butcher” |
Special note: “RIP: HERD, FISH, RUBINO”
“The syntax refers to an inside joke where we supposedly gave our lives in an effort to get the FCC production board done in time, after being informed just the week before by a middle manager that all the work on the C128 must stop as this project has gone on far too long. After the head of Engineering got back from his business trip and inquired as to why the C128 had been put on hold, the middle manger nimbly spoke expounding the virtues of getting right on the job immediately and someone else, _his_ boss perhaps, had made such an ill suited decision. The bottom line was we lived in the PCB layout area for the next several days. I slept there on an air-mattress or was otherwise available 24 hours a day to answer any layout questions. The computer room was so cold that the Egg McMuffins we bought the first day were still good 3 days later.”
The 128 went on to be a notable success for Commodore but not because of its new power. Unfortunately most software developers ignored the new and advanced C128 Mode functionality. Why develop software for a new, relatively small product like 128’s native mode when you can write software for the wildly successful C64 and know that your code will function on a C128 operating in C64 mode. There were some notable exceptions, such as the Graphical User Environment called GEOS which created a powerful C128 Mode version.
The last gasp was a very small production run Commodore 128CR’s (Cost Reduced) released in North America in 1988 or 1989. They were identical to the 128DCR except they did not have an integrated floppy drive. These are so rare I have never seen one of these units… not even a picture until the awesome Steve Gray sent us his:
One of readers, Dominic Pessagno, told us:
“The 128CR has metal joystick ports, torx screws instead of philips screws and the later ones has expanded video ram. Other than that, they look exactly the same”
If you have one, please email a picture to us and we will add it to this site with credit to you.
On a sad note, the 128’s CP/M Mode was almost never used because CP/M was quickly losing ground to Microsoft Disk Operating System (MS DOS) by then running at version 2. MS-DOS was of course popularized by the IBM PC and seemingly endless number IBM clones. Business developers had all but abandoned the old standby CP/M in favour of the new and rapidly expanding DOS market. The Commodore 128 was CP/M’s last big play, but the 128 just did not have the market penetration to keep CP/M alive.
“The 128 Remastered” went on sale in December of 2018 at the128rm.com for €259.90 and were terminated in 2019 with deposits being refunded without explanation.
We contacted the designer at the end of November 2018 and Peter provided us with the pictures to the right (which are 1 version out of date) and told us:
I am currently waiting for the manufacturer to finish, hopefully the last version. I am thinking of to start the pre-order this year. Reseller’s are welcome! 🙂
I think we don’t have any legal issues. I am not using the Commodore brand name and using an modified version of the schematics. So there shouldn’t be any.
NEW V2 – Commodore 128 Diagnostic Cartridge 785260 GOLD ENIG C128 128D 128DCR in stunning black! This new Version 2 of our 128 diagnostic cartridge features a decoupling capacitor on board. It exists to filter undesired noise from your power supply.
This is uniquely designed specifically for the Commodore 128/128D/128DCR operating in 128 mode! That’s right, this diagnostic cartridge will test your 128 while operating in 128 mode… not 64 mode.
Prototype Commodore 128D Plastic Cases
Images courtesy of Bo Zimmerman and his amazing zimmers.net Commodore site THANX BO!. Original source for these graphics was Maurice Randall.
This C128 page is sponsored by Electronic Tips at EntitleBooks.com
THANKS!
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View Comments
C128 was my first computer and back then I had a lot of fun playing games (in C64 mode) and doing BASIC programming in C128. Little machine language exercises out of computer magazines.
I am reading here C128 specs and they aren't really true. C128 is 1MHz only, not 2MHz, Z80 is only 2 MHz, not 4MHz and CP/M only 8 bit which was back then dead already since a while.
Why all defect parts and lost souls were pushed inside of C128 is a mystery (and probably nobody will ever be able to explain it understandably)
I am talking about really useable frequency.
Sure, we have a decent computer with C128 despite all the unnecessary extras and even being slower than C64... It's still fun :-)
I just can't stop thinking what would have been out of Commodore and C128 if they made 4 MHZ C128 and have C64 1 MHz compatibility mode added on top of that.
Okay, people, now wake up and create 4 MHz C128 ;-) and compatible VIC 5 chip with 32 colors (out of 256 color palette)... Hehe...
I have a Commodore 128 that I bought used on eBay. I have installed JiffyDOS in it and I also own a Commodore 64 breadbin, a 1541-II, a 1571 and a 1581. Yes, the Commodore 128 was a versatile machine. Too bad Commodore messed up on marketing the computer. It would have been a serious contender when compared to computers double the price.
Hi Jon;
So true. Bad management worried about milking profits in an R&D business is just a formula for failure. It is a tribute to how successful the company was, that it took nearly a decade to die after Jack Tramiel left.
Great article! Thanks for sharing.
Commodore 128 is one of the most amazing things that I've seen. I never thought that an antique like this would be worth so much. The person who made the Commodore 128 must be a genius.
Bil Herd is the primary system designer of the C128. Dave DiOrio was the designer of the VIC-III and MMU chips. Yes, Bil is a genius. I was his #2 on the project, and I leaned about as much about computer design -- particularly the real-world stuff they don't know to teach -- from Bil as I did in four years at university. We're still in touch... I drove with him up to VCF East last year.
Thanks Dave!
If you want to check out C128 CP/M with sound and graphics then check out https://github.com/sgjava/garage/tree/master/commodore/cpm
Is there any way I can save my old games and programs into new storage?
This can be done but it requires some work. If you post this question in our Forum, several people will help you :)