Posted By
beholder242
on 2025-10-26
14:02:19
|  Undocumented Low-RAM character displays on DIAG264
Good afternoon all,
I'm working on fixing a Plus/4 that very clearly has RAM problems due to random characters showing up on the screen when powered on.
I've opened up the machine and running Diag264 on it, however, I'm seeing some characters on the screen and some behaviors that are not in the documentation.
Amongst all of the @ characters, I do see several A's, B's and reversed @ symbols, indicating the RAM chips at U11, U12 and U18 are bad. So far so good. But along with those, I'm seeing some flashing reversed @ symbols and a reversed @ symbol that is a bluish color instead of yellow like the rest of the characters on screen. These two cases are not covered in the documentation that I can see. What do these cases mean and how should I interpret these?
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