DEC bus transceivers

Noel Chiappa jnc at
Wed Oct 26 11:40:23 CDT 2016

Re: DEC bus transceivers
    > From: allison

    > Actually since about 1987 I've used about 1200 pieces of the 8641 alone
    > repairing boards at the commercial level.

Well, that's over almost 30 years - and your total from that period is about
4% of the remaining stock (and in a commercial operation, to boot, not

    > If you going to build a board or three maybe even 20 its not a big deal
    > but its not a reliable source of predictable quality.

Sure, but try looking at it from our perspective: we either use an
out-of-production part, or have to design something (almost certainly from
discretes) that meets those specs; and we actually looked at the latter (viz.
Dave B's design). However, after some pondering, and taking everything
(including all the below) into account, we decided to go with the original
chips, since they were still sorta available.

Which is why both we and Guy have stocked up on them, at the start of the
process: we don't want to crank out boards designed for a certain part, and
then not be able to get the out-of-production parts the boards were designed
to use.

If we were designing something for serious production, that wouldn't be an
option, but for limited-volume hobbyist use, it is. The choice of an
out-of-production part does have a down-side, but it's minor (and mostly
alleviated by the pre-buying), and the other options were (in overall sum)

    > If you get to the bridge your talking redesign in reality or an
    > expensive buy from unreliable source then testing them in bulk.

But, but... I'm _already_ buying them from unreliable sources, then testing
them! :-)

But to be serious - if the demand for QSIC's, etc, runs the well of DS8641's
dry, yes, we'll probably have to re-design. In other words, we'd be right
where we'd be today if we decided not to use out-out-production parts.


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