Pr1marily Contented (Longish)

From: Douglas H. Quebbeman <>
Date: Tue Apr 2 18:43:14 2002

> "Douglas H. Quebbeman" wrote:
> > Now that my Prime 2455 is fully operational again,
> ...
> > Ok, go for broke, swap in the remaining CPU board set, replace
> > newly-provided CPU board interconnects (top hats) with my old
> > ones...
> Thank you! Thank you! You've solved a twenty-year-old puzzle
> for me and all the other Prime hackers at Westfield College.
> You see, one day we were bored enough to read the Prime 750's
> log book (must've been a day when the power failed or something)
> and the Prime engineer had written the inscrutable:
> Rotated top hats
> Now, we didn't know what these gadgets were, but rotating them
> seemed to be crucial to making our beloved Prime work, so we
> just accepted it. Every time an engineer called, we'd look at
> each other and say "He's here to rotate the top hats again".
> Now, at last, we know what they are! Any chance of a photo?

heh, believe it or not, there are two different, unreleated
things called "top hats" in some Primes... In my 2455, at
the top, underneath the removable top skin, is a small +/- 12VDC
power supply, called the "top hat PSU".

But the 750 wouldn't have had those... in the link below,
they are the three small rectangular vertically arranged;
my 2455's boards run vertical in the cage:

OTOH, in the 750, the boards went in horizontally, so
you'd have seen the top hats left-to-right (at least
that's how they were in the P400 and the P650).

Glad I could help!

-doug q
Received on Tue Apr 02 2002 - 18:43:14 BST

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