BETSI Expander for the Commodore PET

william degnan billdegnan at
Mon May 8 20:02:39 CDT 2017

On Mon, May 8, 2017 at 8:35 PM, John Ball via cctalk <cctalk at>

> So it seems in the early days of the PET a company by the name of
> Forethought Prouducts sold an expansion module called the BETSI which
> plugged into the expansion bus of the PET and gave you four S100 slots. If
> you google around you can find a flyer advertising the unit and optional
> power supply and the owners manual which touches on assembly, component
> locations and the schematics. It talks about adding sound voards,
> additional
> video outputs, expanding ram and attaching directly to a larger S100 frame.
> Beyond that I can find absolutely nothing else about it, much less a more
> recent photo of one. Has anyone here ever used one? How practical were they
> in reality? Suppose I went and built one. Does anyone have the PCB layout
> templates so I could get a board etched or will I have to stick to the
> schematic and build one by hand?
> -John
At VCF SE Don French talked about the S100 expansion he created for the TRS
80 Model 1.  Guess these did not meet with much success.

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