4Kx1 static RAMs...

From: Tom Jennings <tomj_at_wps.com>
Date: Wed Dec 22 19:06:57 2004

My old machine is slowly becoming sensible.

Turns out I had three bad RAM chips in my Seattle 16K
boards. They're TI 9044's, I assume are 2147 type. Jameco sells
them for $6 each; is there a better source? (They're also 55nS
claimed, about 3X faster than what's in there now!)

I juggled chips such that the duds are at 9000 - 9fff, so I can
boot CP/M (62K system) and run some programs (memtest, sid...).

I've got to figure out why the floppy controller won't talk to
side 2 (sectors 27 - 52) and I can do that in 16K easily.

My B: drive is loud OH MAN IS IT SO LOUD I have to power it off
after a program load! Need to find another double sided drive.

Out of sheer laziness, to avoid even the faint effort it took
to find the bad chips, I yanked all my nice static RAM and
swapped in my other RAM cards, one by one:

* Central Data 64K
* MSC 64K
* mumble brand, some acronym, no manual (I'm not at home right now)

My EPROM monitor resides at 7800 - 7fff, uses a dozen bytes
RAM below 7800. It self-copies into RAM and turns itself off
(for a clean address space after boot).

Central Data: set the jumpers right, plugged it in, Nothing
Happens. (Boring story & expletives deleted) it shorted +16V,
popped the fuse. Another one of those !_at_#$%W^% tantalums;
47uF/35V. Replaced with an electrolytic (it was just down near
the card edge). Card works now, but flake-ey results, failed
address-contention tests, couldn't boot CP/M. It's all 4116's,
lots of jumpers for buss timing, ugh. Needs Work.

Reference separate rant on capacitors.

MSC: Dislike this thing's RC filters on the data/address
lines! Crock-detect! I forget the problem, but had problems
with one bank (32K).

Mumble: Inert.

All the static cards back in, debugged the problem. For the
S-100 buss, I'll stick with static memory, thank you!
Received on Wed Dec 22 2004 - 19:06:57 GMT

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