26 Oct
2016
26 Oct
'16
4:38 a.m.
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:
http://ana-3.lcs.mit.edu/~jnc/tech/QSIC/TestCardF.jpg
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.
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.
Noel
26 Oct
26 Oct
5:15 a.m.
On 10/26/16 7:38 AM, Noel Chiappa wrote:
I
have those too. You need them to maintain DEC cards.
Then again I have a few of the chipkit proto cards too.
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:
http://ana-3.lcs.mit.edu/~jnc/tech/QSIC/TestCardF.jpg
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. 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.
Allison
Noel
5:43 a.m.
On 10/26/16 7:38 AM, Noel Chiappa wrote:
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.
Noel
Actually since about 1987 I've used about 1200 pieces of the 8641 alone
repairing boards
at the commercial level. Up till recently I had a side business keeping
commercial in use
pdp-8 and pdp11 system in NC machines. Subs are not possible in that
case as its all
about pin out and form factor. Same for unique no-DEC boards in that
service.
There is no choice for them, it has to fit the same hole. And most of
the 11s were Qbus
as the Unibus machines even minimal sized ones were generally large.
No they are scarce, any parts are NOS(new but old stock) of an out of
manufacture part.
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. If you get to the bridge
your talking redesign
in reality or an expensive buy from unreliable source then testing them
in bulk.
Allison
2979
days inactive
2979
days old
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