On Thu, Feb 1, 2018 at 2:41 AM, Francesco Messineo <francesco.messineo@gmail.com> wrote: > On Thu, Feb 1, 2018 at 2:47 AM, Mia Magnusson <mia@plea.se> wrote: >> Den Tue, 30 Jan 2018 23:53:46 -0500 skrev Ethan Dicks >> <ethan.dicks@gmail.com>: >>> That's what I'm doing for my 2001-8. I don't have enough working >>> 6550s to run an 8K machine, so I have a single 62256 on a CPU socket >>> board strapped for 8K. >> >> Did you remove all main RAms on the motherboard, or do you use some >> other method to make it not collide with the 62256? > > on a 2001 board, it would collide anyway because the 74LS244 on the > RAM data bus are enabled. In case it's not clear, I was not implying I made my own board with only a 62256 on it. I have several of these: http://vic-20.de/x1541/hardware/petram.html > On my PET RAM/ROM board (my own design as always) there's 74LS245 > between the internal RAM/ROM, 6502 data bus and the external data bus > that's enabled only when the 6502 makes access to external addresses > (configurable). Yes. Nicholas Welte's design has a '245 for data bus buffering, and a GAL for deciding what accesses are onboard and which ones get passed through to the motherboard. As I said, I don't have a ROM installed in mine because I happen to have a full working set of original 6540 ROMs, but I can easily install multiple PET ROMs via a single 27256 if I decided to. -ethan Message was sent through the cbm-hackers mailing listReceived on 2018-02-01 20:00:02
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