MEM11 update

Noel Chiappa jnc at
Mon Feb 8 16:04:51 CST 2016

    > From: Guy Sotomayor

    > The reality is that an SPC board will be more expensive because of the
    > gold edge fingers.

Oh, right, forgot about that. Yeah, six of one...

    > I was originally thinking that if I do have to split the board up, that
    > I'd make them completely independent. But that has the issue of
    > requiring 2x the number of UNIBUS transceiver parts (which are all but
    > unobtainium as of now).

Actually, 8641's (at least) are still around for not much. See below.

    > some of the signals I'm running are pretty fast between the FPGA and
    > some of the other components ... I wouldn't want to run those signals
    > very far and certainly not across any sort of cabling.

For sure. We've been having issues (although we think we have it licked now)
with signals running across a flat cable between the prototype QSIC's
mother-card (a QBUS wire-wrap card) and its daughter-card (an bought-in FPGA
devel card), and that's for much slower signals (the only thing on the
mother-card are QBUS transceivers and level converters). Of course, the fact
that the interface doesn't put a ground wire between each pair signals wires
doesn't help! :-)

    > From: Ethan Dicks

    > I'm starting to get sorry I sold off my surplus NS8641s from Software
    > Results 20 years ago. To be fair, I did get over $4 each for them, so at the
    > time, it was a good deal for me (ISTR retail was $7.50 even then, so I
    > got a good spread on the price).
    > I do have some left, but handfuls, not armloads.

NS8641's are still available. I got a bunch from a guy in Hong Kong for
US$1.50 each - considering the source, I built a test card to make sure they
met specs, and they do, so I'm pretty sure they aren't counterfeits. :-)

When I was worried he couldn't find enough, I checked with a supplier (4 Star
Electronics, I think) and they had like 50K available, and quoted me a price
in about the same region, so I don't think UNIBUS transceivers actually are a
problem, at least, not at the moment.


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