I'm sure I've seen this covered somewhere but I can't find it - so...
Does anyone know the pin-out of the 28 pin socket that sits under my 24 pin ROM?
The board has 28-26 shorted together which makes me think this might suit a 27c64 eprom... However that thought soon disappears when I check the rest of the pinout.
It looks like I'm going to have to wire up an adapter:
socket[18] re-routed to EPROM[23] (a11)
socket[21] re-routed to EPROM[2] (a12)
socket[20] joined with EPROM[20] (/OE+/CE)
Of course I could re-arrange the data in the ROM so that I didn't need to rewire a11 & a12. But that would only reduce the re-wiring by 1 connection.
According to my notes, pins 1, 26, 27, and 28 are all Vcc and pin 2 is A12. I once used a 2764 in the socket without adapter but, IIRC, only 4K were usable.
I haven't been able to find one. I think I might prefer a second option right now though; Littlejohn's posting about his 32k upgrade has made me think about putting ROM in the 8k block..