[ale] cpu underclocking

Thu Dec 19 14:32:27 EST 2002

I have worked in electronics for around 12 years.   I remember a service
call in Atlanta where I replaced a fuse in a big screen TV and turned it on.
It started to whine and increase in volume while the customer watched with
bulging eyes as the whine ended with a deafening explosion.
After the smoke cleared she looked at me and said "It's never done that
before"
As I picked up pieces of the flyback transformer, I told her "You can bet it
won't do it again."

About once a month or so I would get a good shock.  Kinda wakes you up!
Especially if you experience flying without an airplane!

The power supply used in most VCR's and computers is a sweep mode power
supply.  It holds the 5v and 12v steady within a very small parameter
regardless of current.  If you attempt to lower the voltage by adding a
resistor it will increase current to raise voltage.  If it cannot raise
voltage, it shuts down or smokes. It is not advisable to lower the system
voltage at the power supply to the mother board.  There is a small range of
voltage difference between a "0" and a "1." If you get a one below the
threshold and above the zero, it will not be predictable what it will call
it and you will get too many error at the very least.  However, you can
connect the fan to the 5v line instead of the 12v line and there are
adapters to do that or just move the molex plug to the 5v pin.

 If you really wanted to run the system on a lower voltage on the
motherboard, you would have to change the value of a regulator diode in the
power supply.  Also get a motherboard that has low power requirements like a
Micro-ATX or smaller to do it.  Just because an overclocked system requires
a higher voltage doesn't mean an underclocked system would require less.  I
think Delta still has those $8 Micro -TX MB's.  The micro-ATX boards require
a smaller powersupply like a 150Watt.  They are also cheaper.  Add in a
Zalman heatsink (CompUSA has them without the brand name) and you may have
something you can use.  Change the fan to a 120mm or a 168mm and make it
work at 5v.  That would be a pretty silent system with forced airflow.

If you wanted to use a system you currently have you could reduce the
multiplier on the microprocessor but I don't think it would reduce the heat
much. I think if you want silence the best thing to do is use as much
passive heatsink as possible.  You could replace the current heatsinks with
bigger ones and maybe even remove the fans altogether if you use the heat
itself to draw fresh air into the case.  Maybe you could get a heatsink that
has a heat pipe in it and attach it to the chassis or a part of the case as
long as it is electronically isolated.  Don't the cube Apples use all
passive heat control?

What is you aim? To have a completely silent system or a thermally
minimalist computer?

----- Original Message -----
From: "F. Grant Robertson" <f.g.robertson at alexiongroup.com>
To: ale at ale.org
To: <ale at ale.org>
Sent: Wednesday, December 18, 2002 7:16 PM
Subject: RE: [ale] cpu underclocking

Hahah, reminds me of a quick story of stupidity from my own past..

I've _always_ taken things apart..  since I was really young.  When I was
about 13 or so I got into building and fixing pc's, and by 16 I was doing
all sorts of crazy stuff....

So, I was attempting to change a noisy fan in a power supply one time, and
god only knows why but I still had it plugged in to wall power as I'm
pulling leads off the switch.  (old, AT style minitower).  So, I'm very
carefully removing the thing, with the supply in one hand and the switch
leads in the other and I dropped something.. Quick non thinking reaction was
to drop what I had in the left hand and try to catch what was falling off
the desk..  Unfortunately, what was in my right hand was the switchleads,
and when gravity took over they contacted the metal (read grounded) case of
the supply.. which was still plugged in, as I said before.  Blue sparks,
quick whiff of ozone, and silence.  Scared the be-jeezes out of me, and blew
power to most of the second story of the house. (thank god for breakers..)
thankfully all it hurt was my pride but, I was always really careful after
that.

Buy me a beer sometime and I'll tell you about fixing monitors in a very low
humidity shop in the winter..  Ouch, talk about aversion therapy.

-G

-----Original Message-----
From: ale-admin at ale.org [mailto:ale-admin at ale.org]On Behalf Of Stephen
To: ale at ale.org
Turner
Sent: Wednesday, December 18, 2002 6:38 PM
To: ale at ale.org
Subject: RE: [ale] cpu underclocking

> Disclaimer : This is off the top (over the top?) brainstorming.. might
> work, might not..  If you blow anything up or hurt yourself (the inside
> of a power supply is not something you wanna be playing with if this is
> your first attempt to hack hardware), don't come crying to (or sue) me.

if i blow up a powersupply (again) or shock the snot out of my self then i
deserve it for being careless :-p besides, im the nut whose doing it! no
ones putting a gun to my head.. atleast not that i see.... never know if
theres a sniper outside in a tree or not :-p speaking of blowing up
powersupplies, i wish i still had mine, blew the capacitors cap clean off!
coolest thing ever! some smoke loud bang all from using an old power
cable... go figure,

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