[ On Friday, March 30, 2001 at 00:16:40 (-0500), Andy Ball wrote: ]
> Subject: Cooling
>
> Either way, my own feeling is that a vertical card-cage,
> with either convection or forced-air cooling, is preferable
> to the majority of PCs I've seen, where air is dragged in
> via any available orifice, swills about the case haphazardly
> (possibly being sucked through the microprocessor cooling
> fan a few times) before being blown out of the PSU's exhaust
> port.  If any breeze gets between the cards, it's more often
> by luck than good judgement.  I even hear horror stories of
> machines that drag air in through the PSU, and then blast
> hot air over the mainboard.  :-(

Well most modern PC power supplies run very cool anyway, so the ATX
specifications for fan and air flow actually make sense.  Some
"high-end" ATX power supplies include two fans, one on the back pulling
the air in, and another on the side facing the CPU blowing air out.
They have enough air flow that the temperature gradient through the PS
is very low.  At least in an ATX machine the CPU(s) is(are) oriented so
that the air flow is directly across them.

I generally glue or otherwise mount a small fan in front of the cards in
any machine that ends up with any number of high-energy cards (eg. some
network cards, etc.)

Of course most "industrial" systems have a fan pulling air in on the
front of the chassis too (well even most PC tower machines have mounting
for such a fan too, though only "high-end" ones include the fan).  Some
industrial machines have a bank of fans behind the drives and in front
of the motherboard and cards.  That fixes the problem no matter how many
cards you have or how long/high they are.

Traditionally keeping drives cool has been much more of a problem than
most cards (you only run into trouble if you have fully populated
slots).  For example the original 10k RPM Cheeta requires 80 CFM of air
flow past it in order to survive (and presumably to meet warranty
conditions).  Some older Atlas and Barracuda drives were even more
demanding though the Cheeta was one of the first where I noticed that
the installation manual explicitly stated the air flow requirements.
These air flow volumes are almost impossible to achieve in any
traditional PC chassis, and even on some industrial machines (at least
without using those "bay cooler" fans now available).

Modern LP 3.5" drives have gotten a lot better (though I've not yet seen
anything on the new 15k rpm drives).

> Hmm... I wonder if I can offset the cost of the power
> consumed by a VME machine against savings on my heating
> bill!  (great in Winter, I don't really want to think about
> summer ;o)

I'm sure my power consumption does help the gas bill a bit...  :-)

I've had friends who ran lots of big old suns and who had to run air
conditioners even in drafty old warehouses in the depths of winter.

>  A 3/x80 appealed to me a lot because I could
> bung it in a rack with other equipment.  It would take a lot
> more room than a 3/60 though, and presumably drink more
> current (what are the Volt and Amp ratings stamped on your
> 3/280?)  There's probably a point where the lines cross
> though, and a x80 chassis would start saving me space and
> inconvenience (assuming I could find one).

Well the 12-slot will draw more power simply because it's got more fans
to spin (though I suspect my use of twin 10" 115vac cabinet fans was
more economical than running the 12vdc fan tray, especially since I'd
still have needed one 10" cabinet fan anyway).

The power supplies on the 12-slot 3/2x0's are rated at somewhere between
750 and 950 watts (depending on exact model, year, etc., IIRC).

The twin 10" fans were also much less noisy.  I added six 4" fans to the
top of my current cabinet and they're incredibly noisy (but nice and
breezy! :-).  Even they can't keep the UPS in the bottom cool enough in
the summer though.  I really need either central AC in the house, or at
least an air conditioner ducted into my server room for the summer.

The reason it's out in the garage is that it's just too power hungry and
too slow and too hot.  I've now got orders of magnitude more computing
power with somewhat less power and heat.  My whole server room now runs
on two UPS's totalling 1700VA (though I'm adding another 1400VA unit as
soon as I get a new battery for it because I'm maxed out and I've got
one or two more servers to add).

> Not to mention the occasional floating cat.  That reminds me
> of a tale, but I'll save it for a month when the list is
> really, really desperate for content ;o)

:-)

(Most of the floating hair in the old place came from the couple of
months when we boarded the inlaws Himalayan.  We never got rid of all
the hair and I'm sure some of it moved with us to the new place!  He was
hard to keep brushed because he was scared of the other cats and the
strange place and kept hiding.)

-- 
							Greg A. Woods

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