Re: PET II questions (P500, B128, B256)

From: Nicolas Welte (
Date: 2001-12-12 11:26:59

William Levak wrote:
> There used to be an adapter board that would replace 4 6550s with 4 2114s.
> I think it was made by Skyles.  Even when the original PET was still in
> use, it was cheaper to buy the adapter and 4 2114s, than replace 2 6550s.

Today I would use an even simpler approach: Remove all RAMs and ROMs (except
video and character) from the board, and connect a single 32kB SRAM chip and
a single EPROM to the expansion connector. Would eat a lot less power than
the original circuit, but of course it would also look a lot less original.
But it would leave a lot of spare 6550 chips for the video RAM, and only the
character ROM would have to be replaced with an EPROM on an adaptor socket.
Switching between ROM versions would also be very easy. Maybe I'll take this
approach for the dead 2001 board.


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