Who's rewired their house for this hobby?

Jon Elson elson at pico-systems.com
Tue Nov 25 20:58:03 CST 2014

On 11/25/2014 03:17 PM, Eric Smith wrote:
> On Tue, Nov 25, 2014 at 2:02 PM, William Donzelli <wdonzelli at gmail.com> wrote:
>> Well, yes, of course. Which leads to the question why DEC did not go
>> that route. I guess the KL10 power supply people were drunk (again).
> Last year I went to lunch with a friend, and he introduced me to one of his
> friends, who had worked for DEC for a long time. We got to talking about
> various DEC machines, and I mentioned that I was surprised about an
> aspect of the KL10 design. To my astonishment, he replied, "The reason
> I made that decision was..."
> He probably wasn't involved in the ECL power supply design, but next time
> I see him I'll ask.
I'd love to know the story, if he does know it!
> I have heard from multiple sources that DEC made it a point never to design
> machines that actually needed a "machine room".  Even the KL10-based
> systems and the VAX 9000 were intended to be usable in an ordinary office,
> though that was rarely done in practice.  Perhaps the use of 400 Hz power was
> considered to make that significantly less practical.
Well, many machines by many makers didn't actually NEED a 
"machine room".  On the other hand,
the power dissipation and fan noise of the KL10B was QUITE 
considerable!  And, the noise and
massive jets of air from the back of a VAX 11/780 were also 
not quite consistent with an
office environment.  I know (the hard way) that a VAX will 
run in 90 degree F air for a very
long time.  I think we got our up to 130 F once when the AC 
crapped out on a weekend.
The VAX was in the home of the former KL10B with a 
trouble-prone Liebert cooler.
We had a thermostat wired into the emergency power off 
button on the wall and set it to
dump the power at 90 F.  Often we'd run in, notice the AC 
was down, shove the thermostat
as high as it would go and try to restart the AC system, and 
then do an orderly shutdown
if the AC couldn't be brought back online.

This machine room was kept quite clean by the AC, which was 
good for the disk drives.

Oh, many of the larger machines, such as KL10's and 
early/big VAXen needed the raised
flooring for the cables, which would become a HUGE mess 
without. The VAX 780 was
nice as all the "main box" cabling was internal, but if you 
had massbus drives, you
ended up with big snakes running all over.


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