I got a pair 30pin memory
Both sides are populated with 9 chips
No ideia about the size.
I will be glad for any help.
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Googling for 50256cp yields the datasheet, it's a 252144 bit chip. There's 8 per side (+1 parity) , so that's a total of 512KB. 150ns.
That matches this site, which offers a similar stick that's populated on one side as 256KB https://ram-co-shop.de/256-kB-Simm-30-pin-wit … i-HB561003BR-12
512KB with parity if there are 9 chips on each side
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That's uncommon size of 512K, I rarely heard of these or ever seen one. 256K, 1M and 4MB yes.
Cheers,
Great Northern aka Canada.
512K double sided was not the most common, but I remember them back in the day.
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Constantly being worked on. Feel free to message me with any corrections or details of cards you would like me to research and add.
The official 30-pin DIP pinout does not support double-sided modules (i.e. there is only a single /RAS and no bank select signal). I agree with the previous posters that the chips are 256k x 1, so the capacity of the chips add up to 512k x 18, or two banks of 256k x 9. I guess these modules work at full capacity only in selected hardware that repurposes one of the excess address pins (256k x 9 only needs 9 pins, but there are up to 12 address pins in the 30-pin pinout) as /RAS2, just as PS/2 simms have separate /RAS signals for both sides. Maybe these modules are not compatible to the standard PC memory pinout at all.
As usual with small PCBs that (mostly) contain only traces, you can use a continuity tester to buzz out the connections. Datasheets for 256k x 1 RAM chips in that case are readily available, and RAM chip pinouts are mostly standardized.
