Tall Tree Systems`JRAM-3'

From: Robert Schaefer <rschaefe_at_gcfn.org>
Date: Sun Dec 2 13:45:15 2001

----- Original Message -----
From: "Tony Duell" <ard_at_p850ug1.demon.co.uk>
To: <classiccmp_at_classiccmp.org>
Sent: Sunday, December 02, 2001 01:34 PM
Subject: Re: Tall Tree Systems`JRAM-3'

> >
> > Anyone know what this is? It came from a 256K IBM XT, I thought at
first it
> > was a video card, (it was in the first slot), but it's got eight banks
> All the slots on a PC/XT are identical, apart from slot 8 (which has the
> well-known 'pull B8 low on reads from this card' problem). There is no
> reason to assume that the card is slot 1 is video. Nor is there any
> reason to assume that a video card in a PC/XT is MDA (or CGA for that
> matter). It could be almost anything.

Well, I made a few mistakes. I think it's a PC, not a PC/XT. Five 8 bit
slots, a DIN tape port on the back, fully populated with 4 banks of 9 4564.
It is a MCA video card, the `black and white/parallel' was a dead giveaway.

> > nine 41256 ram DIPs on it. That sounds like a lot for a mono video
> 8 rows of 9 41256s sounds like 2Mbytes of parity-checked RAM. That's too
> much for an 8088 to address directly. So this is probably some kind of
> paged memory board, quite likely to be so called 'expanded memory'.

That's a lot bigger than I expected! The board has only 74 series logic on
it, apart from the ram, so I guess all support for the ports on it are
contained on the daughtercard. A closer look indicates that all the readily
visible traces coming from the ports end up on the single-row header.

> If those chips are not on the board, then maybe the external connectors
> just link to the row of sockets on the PCB near them, and you need the
> daughterboard for any I/O functions.

Yup, that's my current guess too.

the chip I broke is marked `D8284A' & `8404HKP" & with the AMD symbol. Any
chance that is something non-essential that won't keep the board from
> -tony

Received on Sun Dec 02 2001 - 13:45:15 GMT

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