Commodore SuperPET

  • Posted by Mike Naberezny in Hardware

    I’ve been spending more of my free time recently restoring vintage computer hardware. I am interested in Commodore 8-bit equipment, from the PET/CBM line through to the 64/128 home computers. I think it’s important to preserve computer history to remember the machines that got us where we are today.

    Since much of the hardware I restore is over twenty-five years old, at least half of it is not working when I receive it. I try to repair everything I can when it’s practical. My Flickr photos page has daily progress of my chip-level repairs on this equipment.

    Recently, I received a Commodore SuperPET computer. This is a remarkable machine that was a collaboration between Commodore and the Computer Systems Group at the University of Waterloo in Ontario, Canada. The SuperPET is a standard Commodore PET 8032 computer with an internal expansion that adds a powerful Motorola 6809 microprocessor, an additional 64K of expansion RAM, a fast 6551-based RS232 serial port, and custom Waterloo software in ROM.

    The SuperPET can operate in MOS 6502 mode, where it is a Commodore PET 8032 with the extra 64K expansion and 6551 ACIA. Curiously, this 64K expansion memory is not compatible with the 8096. A switch on the side puts the SuperPET into 6809 mode, where it can run a number of disk-based Waterloo programming languages including BASIC, Pascal, APL, Fortan, and COBOL. When in 6809 mode, a menu in ROM prompts the user to select a language which is then loaded from disk.

    My SuperPET seemed to work when I got it, with the 6502 mode working perfectly and 6809 mode showing the power-on menu. However, after obtaining the disk-based software, none of the Waterloo languages would run after loading. After verifying the disks were good, I suspected the 64K expansion RAM since the rest of the machine seemed to be working. Using technical information from the PET Index on, I wrote several memory test programs to exercise the expansion RAM.

    The expansion RAM is comprised of thirty-two 4116 DRAM chips. A couple of these had become loose from their sockets and my test program found that one of them had failed. I got a replacement from the pick-up counter at Jameco and installed it. Now, my SuperPET passes my expansion memory test and also boots all of the Waterloo languages. It is now fully functional and I’m exploring the Waterloo software.

    One of the most interesting features of the Waterloo languages is how files are accessed. Commodore disk drives attached to the SuperPET are accessed with a filename like disk8/1.program-name which selects unit 8, drive 1. The SuperPET was designed to be attached to a mainframe computer, known as the “host”, through its serial port. Accessing a file like host/program-name would load it from the mainframe if it was running the special HOSTCM program from Waterloo.

    The HOSTCM program was available for VM/CMS and other mainframe operating systems. Beyond that, I’ve not been able to find out much information about it. I would like to figure out the protocol and write a program so that a modern PC could be used as a host computer for the SuperPET.

    If you have any information on the SuperPET or have Commodore hardware you’d like to donate, please contact me.