weird old ROM chips...

Most of the external microcode units I've seen had piggyback receptacles on top the CPU for plugging a ROM into.

Reply to
Ian Field
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"Ian Field" schreef in bericht news:XF19q.122$ snipped-for-privacy@newsfe12.ams...

I know them too but the processors I'm talking about are build of bitslices or lower intergrated logic. They're not only pre PC but even pre micro.

petrus bitbyter

Reply to
petrus bitbyter

always

9100

project!

up.

be

a=20

old

receptacles=20

bitslices=20

Ah yes, 2900 (TTL), COSMAC, and the likes. And there were a lot of hybrids as well with the micro doing the "slow" stuff.

?-)

Reply to
josephkk

On Thu, 01 Sep 2011 10:03:44 -0700, John Robertson put finger to keyboard and composed:

11 address bits makes them 2K x 8 parts.

- Franc Zabkar

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Reply to
Franc Zabkar

I should go through my stuff and sell off the ROM/EEROMS I have from yesteryears.

Jamie

Reply to
Jamie

Ah, 2K X 8...how did I miss that? OK, if you can find the Mostek 1975 PROM manual it covers the Mostek MK28000 which is a PMOS device using

-12/+5 and might well be similar or the same as yours.

Best guess for part numbers are:

EA4900C or EA4900L

Signetics has a PMOS 2K X 8 #2580 that might be close too...

Looking in my 1975 National Memory book I find the 24 pin MM4214/MM5214 (512 X 8) has a similar power layout (+5 & -12) with no ground/common connection! The book doesn't show the wiring, but does say the PMOS device as directly connected to TTL devices and each line has a 10pf cap.

John :-#)#

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Reply to
John Robertson

Weird. More chips I can't find specs for :-)

Reply to
DJ Delorie

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