Commodore introduced the Commodore 128 in 1985 as an upgrade path from the Commodore 64, the most popular model of computer of all time. The 128 addressed the 64’s biggest shortcomings while remaining mostly compatible with its hardware and software. That makes the Commodore 64 vs 128 a natural comparison, even more natural than comparing the 64 with the VIC-20.
As its name implies, the 128 had 128 kilobytes of memory, double the amount of the 64. Because the 8-bit 6502 series of CPUs could only address 64K of memory at a time, the 128 had two banks of 64K.
The most notable features of the 128 were a faster disk drive, an 80-column display, a larger keyboard with a separate numeric keypad, and built-in CP/M compatibility.
The faster disk drive
Commodore had intended for the 64 to have faster disk access, but a mistake in the design of the original motherboard made this impossible without a revision that would have delayed the machine’s introduction. Commodore expected most people would use a tape drive anyway, so they were able to justify it to themselves, mostly. Then disk drives proved more popular than anyone expected. So Commodore addressed the problem in the combination of the 128 and the new 1571 disk drive. In 64 mode, however, drive access slowed down to the same speed as a real 64.
One of the most popular products ever made for the 64 was the fast load cartridge. The combination of a 128 and 1571 disk drive made fast loaders less necessary–in 128 mode. The 1541’s frailties led to lots of clones. The 1571 had a much better track record.
The 1541 worked with the 128 too, but it was just as slow with a 128 as it was with a 64.
Disk drives still connect the same way on both the 64 and 128.
The 80-column display
The 80-column display came via a separate video chip with its own dedicated RGBI video output. It was completely independent of the VIC-II chip. Commodore salvaged this chip from another computer that never came to market. So it wasn’t compatible with the VIC-II. The 80-column display was popular for word processing and spreadsheets, but aside from those and a handful of Infocom titles, there wasn’t a lot of commercial software that took advantage of this capability. Had Commodore used a better known chip, such as a 6545/6845, this may have played out differently.
The 128’s CP/M mode was a bit of an accident. Commodore marketed a CP/M cartridge for the 64, intending to give it access to popular business software. The problem was that the CP/M cartridge didn’t work with post-1983 revisions of the 64. It was one of the few things that worked well on the silver-label 64. Commodore tried to get this cartridge working with the 128, but failed in that attempt as well. Its designers ended up putting a Z-80 CPU on the board itself so nobody would want a CP/M cartridge. The decision was controversial in 1985 and remains so today. But Commodore solved compatibility issues with certain other C-64 cartridges and peripherals by having the Z-80 handle initialization before handing control over to the 8502. Commodore was able to license the CP/M operating system cheaply and the Z-80 wasn’t an expensive chip, so the increased cost of the CP/M capability wasn’t high.
A new Basic
Less controversially, the 128 included an enhanced version of the Basic programming language with graphics and sound commands. One of the criticisms of the 64 was that included industry-leading sound and graphics capabilities but one had to resort to cryptic POKE commands to make any use of them. With the 128, hobbyist programmers could easily create their own programs with graphics and sound. The 128’s commands were generally more intuitive than equivalent 64 commands.
In 64 mode, the 128 reverted into a close copy of its predecessor, with a 40-column screen, slow disk access, the new keys disabled, and the old, limited Basic. The machines weren’t 100% compatible, but compatibility issues were rare.
Commodore expected the 64 to last between 2-4 years on the market. They learned the hard way in 1984 that any direct replacement for the 64 needed to be compatible with it. That’s why the 128 had compatibility with the 64. For that matter, 64 emulators for the Amiga were popular even though the early 64 emulators couldn’t emulate the 64 at full speed.
The 128 never lived up to the 64’s popularity, but it wasn’t really intended to. It did sell 4 million units, which was a lot of machines in the 1980s. No single model of the Apple II ever sold that many units. Perhaps surprisingly, it increased C-64 sales by giving the 64 an upgrade path. People could buy a $149 C-64, and later, when they could afford a 128, they could use all their old software and peripherals with it.
C-64 sales declined rapidly in the late 1980s. But the existence of the 128 slowed that decline by a couple of years. In the end the 64 sold 20-25 million units and had a number of different incarnations.
Commodore only expected the 128 to last about two years on the market. It ended up lasting closer to four, and it sold better than Commodore expected. In that regard, it was very much like the 64, whose sustained success was also an accident. Unfortunately, Commodore was never able to fully duplicate it again. The 128 bought Commodore time until the Amiga was ready. Unfortunately for Commodore, the Amiga didn’t really match the 128’s success, let alone the 64’s.