Intel i2920 IC was Re: Intel Intellec 8 computer?????

From: Dwight Elvey <elvey_at_hal.com>
Date: Tue Dec 7 18:29:05 1999

ard_at_p850ug1.demon.co.uk (Tony Duell) wrote:
> > Also, Tony, there was an error in the reset circuit that
> > caused flaky reset on some UPP units ( most that made it to
>
> Is this a general UPP problem? As I mentioned I don't have the 2920 card,
> only the 2708 and 2716 (I think) ones.

Hi Tony
 When we saw the problem on the 2920, I'm not sure if anyone
looked into the effects on the other parts. I don't think it
would effect the 2708's but that part of the circuit was
vary similar to the 2716 programmer. I might just be that the
2716's were more forgiving of a slight overshot because I
never saw this as a problem on any of the other boards, while
I was there. I found the problem while verifying my test program
for the board. I personally blew up 3 chips before catching
it. I told the guy that was to do the testing, on swing, to not
test any more that evening and a ECR would be done in the morning.
That night he blew up the rest of the limited quantity we
had on hand. His supervisor had asked him to test the boards
and he never told his supervisor that he couldn't because I
had told him that he shouldn't. He got a bad mark on his quarterly
and it took us 6 weeks to get more parts to test with. I'd
have talked to his supervisor but no one knew where he was that
night or if he would be in. I thought it would be enough to
tell the guy that was actually going to do the work but I
guess I was wrong.

>
> > the field with this problem ). Some units were more sensitive
> > than others. If you write back I can describe the problem
> > and what I remember as the fix.
>
> Please do. I don't have the UPP in use at the moment, but I may well use
> it sometime (it's the only thing I have that does 2708s), and I can try
> the fix. I know I have the hardware manual and schematics for it somewhere.

I think I can work from the schematics. It was a problem with reset.
The 4040 had the reset signal inverted from the 4001's and 4002's. The
problem was that the 4040 was released from reset before the 4001's
This meant that the first instruction was garbled. If you look
at the circuit, you'll see that there was a transistor that was
used to invert these two signal. There was enough delay caused
by this slow transistor inverter that is was flaky. What the fix was
is that the reset source was feed through a spare inverter and
the signals were swapped to the 4040 with the rest of the reset lines.
This was found towards the end of the product life so I doubt
that yours has this fixed.
Dwight
Received on Tue Dec 07 1999 - 18:29:05 GMT