Re: Strange 8255 behavior

From: Mia Magnusson <mia_at_plea.se>
Date: Sat, 16 Jun 2018 05:30:26 +0200
Message-ID: <20180616053026.000066a3@plea.se>
Den Thu, 14 Jun 2018 20:49:14 -0500 skrev Jim Brain <brain@jbrain.com>:
> xc95288xl is a 288 macrocell 5v tolerant CPLD.  ~$USD5.00/piece in
> singles.

$USD5 is a bit too near the limit where it starts to be economically
feasible to scrap fully working C64's for parts. (Say that with a PCB,
some various passive components and the assembly work it might land on
$10 for a CIA replacement. That's $20 for two CIA's, and then there is
VIC, SID and PLA that you can get money for, which is scaringly near
the price levels for a C64 with no accessories (i.e. no PSU).

OTOH, for a project like the 8088 card for CBM-II, there are so few
original 8088 boards that the price level isn't that fixed and most
importantly the CPLD emulating a 6526 can sit directly on the 8088
board, removing a small extra pcb and various passive stuff from the
calculation.

For the 8088 board, one or rather two CPLD's might be able to emulate a
6526 connected to a 6525 (or rather 6523, as the 8088 board afaik won't
need the interrupt controller in a 6525, which makes emulation a bit
easier).

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Received on 2018-06-16 06:00:17

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