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512kb x 16 (8 Mbit) EPROM 40pin needed?
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Mp3:
Guys,

I am having so much trouble finding a replacement ROM for this.

40 pin DIP package, 512kb x 16 (8 MBIT)

I am finding a lot in different packages, finding plenty 32 pin and 42 pin, but none 40 pin????

does anyone know a compatible part? Been looking online for a long time. Some one bay listed as 40 pin, but when you look at the picture they're 42 pin  :palm:
amyk:
What is the original part? Is it a mask ROM?

There's the 27C4096 in DIP40 but that's only 4Mbit.
Cliff Matthews:
What about two ($7usd) AT27C4096 piggy-backed? Vpp may not be needed (once programmed). Perhaps fold it under and route pin-2 of the top chip to pin 1 in the socket to determine which tri-state chip you'll read from?
Mp3:

--- Quote from: Cliff Matthews on July 20, 2018, 12:54:29 pm ---What about two ($7usd) AT27C4096 piggy-backed? Vpp may not be needed (once programmed). Perhaps fold it under and route pin-2 of the top chip to pin 1 in the socket to determine which tri-state chip you'll read from?

--- End quote ---

Thanks for this idea. I haven't been able to find any currently manafactured 8mbit 40 pins, so i'm afraid my best bet might be stacking 27c4096. Thank you for showing how to properly stack them, though  ;)

If i can't find any replacement chips to write the images to, i will probably have to go with that, although it will not be cheap, doing 14 4096 roms! (and will have to figure out how to program them correctly.... pre stacking or post stacking?)
james_s:
You could make a DIP carrier board to adapt a surface mount ROM to the pinout you need. If you have 14 ROMs in the same circuit you can often replace them all with a smaller number of larger ROMs on a carrier board.
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