8-bit acorn hardware • Master Compact 128k MOS

I’ve started a new thread from this one as the subject has changed…

viewtopic.php?t=28091

Time now to upgrade the MOS IC to a larger one to use the other rom spaces available.
I need to find or build a very low profile adapter so the lid goes on, the adapters I have for my master 128 work but I just can’t close the lid……

Well I spoke too soon, I was experimenting with a 128k MOS adapter which I had found in a previous hardware post which I couldn’t get to work, so I decided to stick with my homemade one that I used successfully earlier on the above post, but it wouldn’t work. I don’t imagine the failure has anything to do with the first adapter, just a coincidence.
I re-tested my homemade one in my master 128 just to make sure it was ok…. It was fine.

The adapter….. https://www.stardot.org.uk/forums/viewt ... 90#p399290

This homemade adapter…. http://www.adsb.co.uk/bbc/adaptor.html

A good copy of the circuit diagram is here https://github.com/bitshifters/bbc-docu ... ompact.tif

If I use the original MOS with PL12 north, all is well, but….

When I move PL12 south and plug in my adapter I get a long beeeep and nothing else, I’m using a winbond W27C010 with the new larger set of roms in the 4 vacant slots. As far as I can remember, this was the first build I tested successfully earlier… I think… I’ve experimented with many various iterations since, to no avail.

New 128k MOS file, change .txt to .rom
If anyone has a working 128k image I could try that instead, in case i’m doing something stupid.

I traced the 128k line AA16, between IC48, 38, 29, 39, 40 and IC21 for continuity with PL12 south, all ok.
I my master 128 there is activity on IC48 pin 18 when it has booted up, but on my Compact this line is high.

Any suggestions welcome, thanks

Dave

Statistics: Posted by DaveLecky — Sat Feb 03, 2024 7:53 am

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