Re: Todd's ELF-ish gets some more Memory #ELF #Homebrew

Lee Hart
 

taf123 wrote:
Back in the day, RCA offered several CDP1802-based development
platforms... their Microboard line...
The good news is that the board was still basically functional...
The bad news - two of the chips were DOA.
Although I've never seen RCA 89052 anywhere, the RCA manual for this
Microboard says that the replacement part is the MWS5114. Looking at
the supplied schematic, the chips are pin-compatible. The 5114
obviously has one more address-line, but that pin is tied LO on this
board, so the 5114 would just function like a 512 x 4-bit memory.
I suspect that the 89052's were MW5114's that had a bad bit. Rather than throw them out (RAMs were expensive back then!), they used them as 512-byte RAMs.

I hope to attempt a repair of this board in the near future - updates to
this forum when that happens.
I have a tube of RCA MW5114's if you (or others) need any. I also have a couple tubes of 5101's (some RCA, some NEC). :-)

--
Fools ignore complexity. Pragmatists suffer it. The wise avoid it.
Geniuses remove it. -- Alan Perlis, "Epigrams on Programming"
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com

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