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Welcome! The CGRS MICROTECH PEDISK II was an early floppy disk system for the Commodore PET/CBM computer. The PEDISK did not use the IEEE bus like the Commodore disk drives, but instead used a standard floppy disk controller chip connected to the inside of the PET/CBM machine. It could support both 5.25" and 8" standard floppy mechanisms as configured from the factory. The firmware on the board was able to load CGRS's proprietary DOS from disk. Up to 3 drives (all of the same type) were supported.
This is a project to re-create/clone the PEDISK-II board. A group of us got together as a team and tackled various parts:
Mike Naberezny owns a functioning PEDISK-II card with 8" floppy. He has been documenting and reverse engineering the firmware and DOS. His work can be found on his webpage here and on GitHub here. Mike desoldered all the components and scanned the bare PEDISK-II pcb. Mike also recreated the 8" boot disk and wrote utilities to make and manipulate disk images.
Josh Bensadon turned the PCB scans into a schematic diagram.
I (Steve Gray) transcribed Josh's schematics into Kicad and then duplicated the PEDISK-II PCB as close as possible.
Once the main PCB was cloned the group discussed various ideas for modifications. Mike Stein suggested we allow for additional mounting options. We decided that the original board, which was mounted vertically may interfere with other PET addons, like memory expansions, rom expanders, superpet board etc. We decided that a horizontal mounting would be desired so I shuffled around some components and added an option to use a socket header or pin header. This would allow direct horizontal mounting or ribbon cable connection for more flexible placement of the board. Mounting holes were added at the corners for additional flexibility.
I then added additional labelling of components and jumper functions for easier assembly and configuraton.
The final design was checked and sent off to DirtyPCB.com for production. The boards arrived and they look quite good.
Mike Stein, Mike Naberezny, and myself have completed our boards! We are currently doing additional testing. Mike Naberezny's board seems to work fine as a direct replacement for the original board with his original drive. Mike Stein's board was initially working but now seems intermittant. My board seems to have some issues.
You can find Kicad schematics, firmware and documentation on GitHub here. The current Kicad files have some corrections to fix the labelling issues, plus some additional jumpers for enhanced options, as well as a slight change to the mounting options.
Here is Mike Stein's completed board. Mike chose to use the DIP connection to mount the board horizontally directly on the socket. Mike mounted two 1/3 height 3.5" drives in his PET, which act just like 8" drives!
And here is a video of it in action: Clone PEDISK II with dual internal 3.5" drives
Steve Gray has completed his board and is currently testing it. Steve chose to use a ribbon cable to mount, as well as using two different connectors on the cable. This required twisting pairs of lines so that the wiring was correct.
Mike Naberezny has completed his board and it works! Mike chose to mount his with ribbon cable using the same connector on each end (pictures to come).
Created: Jun 8/2016. Last updated: Oct 25/2018, 3:00pm EST
Send comments or feedback to Steve Gray(sjgray@rogers.com)