40 years of the C128: Commodore's last 8-bit attempt

Contents

Forty years ago, on January 6, 1985, the then home computer king Commodore announced the Commodore 128 at the “Winter CES 1985”. In the biggest boom in the computer industry up to that time, innovations were so prolific that two major trade fairs were needed every year. Veterans and technology historians will already be paying attention here: wasn't 1985 also the year of the Amiga? Exactly, and it was not only this ground-breaking computer, also from Commodore, that ultimately became the C128's undoing.

With around 4 million computers sold across all versions, the C128 was not really a flop, but compared to the most successful home computer of all time, it was more of a side note. With the C64, Commodore managed to sell between 12 and 17 million units from 1983 onwards – Today's estimates vary depending on the source. So why was the C128, which was also almost fully compatible with the C64, unable to match this success?

Three computers in one and three problems

There are three main reasons for this: Timing, Commodore's financial weakness and, of course, compatibility with the C64. The latter may sound paradoxical, but it was very logical in the rapidly developing computing environment of the mid-1980s: software developers concentrated on the largest platform, the C64, and left the C128 behind. The C128 could only show off its advantages in C128 mode without any great tricks; if it was switched to 64 mode by holding down the Commodore key when switching on or using the “GO 64” command, it remained as slow as the C64.

All the innovations of the computer, such as the MOS 8502 CPU clocked at 2 instead of 1 MHz and the memory doubled to 128 KByte, were then left behind. This was no great disadvantage for most programs, especially games, as they worked just like on a C64. But you could never really exploit the potential of the machine. Unless you programmed it yourself: BASIC 7.0 in 128 mode was much more powerful than BASIC 2.0 on the C64, including improved graphics and a wider range of commands. Nevertheless, the German Wikipedia lists a considerable number of applications, mostly office software and many from German providers.

CP/M as a late alternative to MS-DOS

And then there was the third mode, which for the first time promised a bit of established professional applications for a Commodore home computer because the C128 could run CP/M, the “Control Program for Microcomputers”. This was launched as early as 1974 and was increasingly superseded by MS-DOS from 1981 onwards. Nevertheless, cross-platform applications such as the powerful word processor “Wordstar” could also be used on cheaper computers than the boring office boxes.

To make this work, Commodore had installed a second CPU alongside the 8502, a Z80 with 4 MHz from Zilog. Because CP/M, unlike the Commodore operating systems – wants to boot a ROM with BASIC – from floppy disk, the Z80 was always active after switching on. If the computer could not find a CP/M diskette, the C64 or C128 mode started. This was actually quite clever, especially as the boot disk with CP/M 3.0 was included. However, due to the design and cost-cutting measures, the computer was much slower than comparable CP/M machines.

This was because Commodore had only designed the Z80 as a processor in itself; the rest of the C128 hardware always had to help out for I/O and graphics. In reality, the Z80 only ran at around 2 MHz, roughly in sync with the 8502. To be able to display the 80 characters with 25 lines that were standard for CP/M software, a new graphics chip, the VDC, was also required. This was an in-house development of the Commodore chip developer MOS, full name: MOS 8563. It was full of bugs, could not trigger its interrupts and was dependent on 16 KByte of RAM, optionally 64KByte. In contrast to today's GPUs, however, this was much slower than the main memory due to its connection, in short: the VDC was not suitable for gaming. It wasn't until later that a few graphics demos appeared, which, with many tricks, still managed to conjure up a lot from the VDC.

Two graphics chips for two different monitors

But the VDC was good for text. Commodore had once again come up with a special feature for this. Unlike the C64, the C128 had an RGB output (RGBi) for monitors in addition to the composite output. This new port was also suitable for the CGA monitors familiar from PCs with their very sharp text display. However, this mainly applied to the USA, as RGB monitors or televisions with 60 hertz and RGB input were not yet widespread in the rest of the world, especially Europe. Thanks to the text mode and the comparatively large memory, the C128 did gain some popularity in the USA for operating a BBS, known in Germany as a mailbox. And vice versa: The terminal program DesTerm for the native 128 mode was also able to display the ANSI representations offered by Unix and PC BBSes on a home computer.

The second graphics chip, VIC-IIe, was largely identical to the VIC of the C64. Both graphics chips could be used simultaneously in C128 mode, making the computer probably the only home computer in its class at the time that could be used with two monitors, for example for programming: The RGB display in 80-character mode for the code, the composite monitor for the output. The rest of the I/O chips are identical to the C64, especially the SID sound chip. As this is still popular with musicians today, some users at the time wanted two of them for more voices, as the C128 is incapable of multichannel real sound output like the Amiga. So, here too, there is no reason to develop special software for the C128 mode.