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agranlund / STRam

4MB RAM expansion for Atari 520ST(M)
GNU General Public License v2.0
42 stars 9 forks source link

Cannot get board to work at 4MB, only 1MB when pulling u15 MMU to ground. #4

Closed Verault closed 1 year ago

Verault commented 1 year ago

Hello. I just finished installing this board On my North American NTSC 520ST. I have the appropriate jumper wire as depicted in your photo. I got the idea to install a switch on the A9 line from an episode of Adrians Digital basement where I found out about your 4MB board: https://youtu.be/uqWCmKcaZtI?t=1487

When I boot the computer, to either GEM or my Atari ST diags cartridge with it set to 4MB I just get screen garbage: IMG_20230911_140555

And if I boot with the same diag cart and have the switch set to pull a9 to ground it works: IMG_20230911_140613

Also on the ADB video it says you need to reverse lines CAS1L and CAS1H they are mislabeled. But I dont see this on the github site. Is that not something I need to worry about? I think I am pretty close to getting this thing working. what do you think? Please excuse the terrible video. I am using a small 9" television and RF on my workbench for testing.

Verault commented 1 year ago

So the issue was my switch. I wasnt using the proper multi pole switch and it needed an additional ground for the a9 line when switching to 1MB. Completely my fault! And I can tell the cas1H and Cas1L work fine as is so I dont know why the video mentions swapping them.

Ran Memory diags in both 1MB and 4MB mode and they both pass fine.

Great board and thank you!