25 Aug
2010
25 Aug
'10
4:20 p.m.
I wrote:
Had we found any problem analogous to that in the
PDP-1 restoration,
where the machine operated correctly despite a manufacturing defect, I'm
sure we would have had a debate on whether to fix it. I think my own
opinion in that case would be that we should leave it alone, but tag the
module (paper tag attached with a short loop of string) and document the
issue in the system logbook.
Fred Cisin wrote:
In the example that I mentioned of an IBM MDA board,
it worked for about
10 years, and then became intermittent. Even that, I would NOT consider
to be "operates correctly", as the particular defect IS a defect, and may
eventually bring the system down.
I think the way that I would state it is that just because the system is
working correctly (at the moment) doesn't mean that it isn't broken.
Part of the reason I don't think we'd fix such a problem in the PDP-1 is
that the PDP-1 isn't doing anything criticial. We can afford to have
downtime if a latent problem eventual causes a failure. If we've
properly documented that latent problem, we can check for it when the
system does fail, and fix it if necessary at that time.
Eric