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286 Epson Equity II+ memory card upgrade question

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First post, by lowlytech

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Have this Epson that has 640k on its BIOS/memory addon card. I would love to get it to 1MB just for giggles. Is there anyway I could replace chips on this board to achieve this? Looks like the chips on the right are higher density that the ones on the left, but noticed they have two extra pins per chip.

Just trying to avoid finding a 16 bit memory expansion card to plug into the ISA like the manual states as the proper way to upgrade the RAM.

Thanks..

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Reply 1 of 3, by Horun

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On a very quick inspection: Nope you cannot easily change out the left 4x64k ones for higher density 4x256 (like on the right) as the board is hard wired for those chips. You would need to put sockets in that are same pinout as the 4x256k and run new traces that match the data and address lines plus do some other major tracing to see if the jumpers J1 and J2 need modifying to enable the extra ram......but I could be wrong 🤣

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 2 of 3, by lowlytech

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Thanks Horun for the info. Wishful thinking on my part, but I guess i will keep an eye out for a cheap 16 bit ISA memory card if one ever shows up. Looks like it will probably be a long wait.

Reply 3 of 3, by BitWrangler

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Non PC systems have mods called "piggyback" RAM upgrades where chips are soldered on top of original chips and address lines are bent out and bodge wired to right bits of address bus. Possibly you'd need to do it on the 4x256s and disable the 64s.

Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.

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