Re: VAXstation 3100/m76 stray interrupt

[Johnny Billquist <bqt%update.uu.se@localhost>]

On 2016-08-21 13:19, Aaron Jackson wrote:
> I am guessing that the 74LS243 is just soldered on the board somewhere?
> Perhaps if I replace it my machine will become much more stable?

Why would only NetBSD be unstable, while VMS and OpenBSD works?

	Johnny

> Aaron
>
>
> Felix Deichmann writes:
>
> > Am 16.08.2016 um 23:00 schrieb Antonio Carlini:
> > > This was when I was in DEC so with a bit of hunting I found the
> > > description of the problem. IIRC there was an issue with the 74LS243 bus
> > > transceivers.
> >
> > Interesting. I evaluated parts suitable as Q-Bus drivers/receivers
> > recently and noticed that for example a TI SN74S38 will quickly reach
> > extreme values for high-Z leakage current (I_OH in the datasheet) when
> > warmed with a heat gun (and become out-of-spec for Q-Bus of course)...
> > Values are even quite different for ICs of the same batch.
> >
> > It could be a similar issue with specific batches of 74LS243, i. e. they
> > will impose an unconsidered load (when the machine was designed) for
> > other participants on the (memory) bus when it gets warm.
> > Especially leakage current can be extremely dependent on temperature.
> >
> > Felix


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Johnny Billquist                  || "I'm on a bus
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