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Cannot use EPROM to replace character ROM in 4032.

I found some Motorola 68B45 CRTC chips in my spare parts collection. I had already tried a few different Hitachi 6545 chips with no change in behaviour, so I tried these. None of the 68B45s worked. I got a single horizontal line in all cases. I don't see any reason why the 68B45 won't work in a 4032, and they can't all be faulty in the same way.

So does this mean that the 68B45 is not compatible with the 4032/8032? (though I have heard of people using them successfully).
Or perhaps my machine has a subtle fault in it where the 6545 crtc mostly works, apart from character EPROM incompatibility and some glitching in 'No PETS Allowed', but fails completely when a 68B45 is used.

Has anyone else successfully used a 68B45 in their PET?
 
Ah yes, for some reason they don't work (I am led to believe - although I haven't tested it myself). No one has worked out why yet, but it is well known here that these don't work in a PET.

Challenge for you is to find out why 😀!

I think @dave_m is the expert here on this.

Dave
 
daver2 said:
Ah yes, for some reason they don't work (I am led to believe - although I haven't tested it myself). No one has worked out why yet, but it is well known here that these don't work in a PET.

Challenge for you is to find out why 😀!

I think @dave_m is the expert here on this.

Dave
Click to expand...
Haha! I still haven't figured out why most of my EPROMs don't work as character ROMs!
 
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