Sunday, 26 October 2014

Commodore 128 Repair - Part 4 Commodore 128 Modes

Having completed testing the Commodore 128, it's time to run through a few of it's features.
It's a bit of a strange beast the Commodore 128, two CPUs, two video processors, four types of memory, three operating systems and two versions of BASIC. Not bad for a single computer.
The default mode on power on is Commodore 128 mode. This has 128K RAM and BASIC V7.0 and uses the 8502 processor, based on the same 6502 as the Commodore 64's 6510 and the 264 series 7501. The default is 40 column mode, it can also work in 80 column mode, but you need to connect the monitor to the 9 pin D connector, rather than the normal 7 pin DIN.
If you type GO64, or hold down the C= key on startup, it goes into C64 mode.
This is limited to 40 columns, and 64K of RAM and runs BASIC 2.0, as did the Commodore 64, again using the 8502 processor.
The third mode, uses the Z80 processor to run CP/M. To use this, you need a CP/M system disk in a 1570 or 1571 disk drive. I don't have one of those at the moment (watch this space), so I'm loading the disk image from an SD2IEC.
This loads up (after a while) into CP/M version 3.0.
It also works in 80 column mode.
That's quite a lot of options.

  • 40 Column Commodore 128 mode
  • 80 Column Commodore 128 mode
  • 40 Column Commodore 64 mode
  • 40 Column CP/M mode
  • 80 Column CP/M mode

I wonder how many C128 owners used all the modes?

It seemed compulsory in the Commodore Pet repair articles to show space invaders, so why not continue that, here in an 80 column Commodore 128 version.