DEC bus transceivers

allison ajp166 at
Wed Oct 26 07:15:29 CDT 2016

On 10/26/16 7:38 AM, Noel Chiappa wrote:
>      > From: Guy Sotomayor
>      > Secondary chip marke[t] (only reputable vendors).
> I'm a little more willing than Guy to troll in disreputable waters (I bought
> 1K DS8641's from a source in Hong Kong), so I have this:
> which has a bunch of special circuits on it to test chips to make sure they
> meet specs; e.g. the large potentiometer is so I can vary the input voltage
> to see where it switches from 0 to 1, etc.
>      > From: Paul Koning
>      > it would be odd to have one; I can't think of anyone who would expect a
>      > PDP11 to work with part of its devices powered down. For one thing, if
>      > the box with the terminator loses power
> Forget the terminator - as Jon Elson also points out (his email appeared
> while I was creating this one), any device which uses interrupts, if
> un-powered, won't pass grants.
>      > From: allison
>      > Bottom line is someday there will be no DEC parts and what then? I
>      > reserve DEC parts for repairing defunct boards for new and unique build
>      > it would be a waste of scarce material.
> For actual DEC interface IC's like DC003's, sure. Those are hyper-rare.
I have those too.  You need them to maintain DEC cards.
Then again I have a few of the chipkit proto cards too.
> But DS8641's are available in the 10's of thousands, there's no earthly way
> we could use them all on repairs. Yes, when they run out, we'll have a
> problem - but I plan to cross than bridge _if_ and when we get to it.
What vendor and price???  They have been scarce save though resellers 
that have NOS parts from
old stocks and they are not cheap and unpredictable quantities.  TI the 
only source when they consumed
National Semi is the listed source has it as obsolete out of 
production.  The second source Signetics
went away decades ago before Phillips consumed them.  Then I could buy 
them they are about
.86 dollar US, but that was in the early 80s.

Every time I see something written suggesting the the 86xx parts are 
magical I go back to the
databooks (National and Signetics from the 70s and the current TI) and 
find nothing that
special or unique.

If you have them great, when you run out I'm not giving up the supply I 
have from DEC.

> 	Noel

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