Tom’s Alpha/Peltier Kits

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Tom (Mr. Peltier) Leufkens has developed two peltier kits, one for the Alpha Celeron/PII/PIII and one for the Alpha PFH6035 Socket 7 cooler. Each of these kits comes with instructions, a 50 watt peltier, screws, backing plates, foam gaskets and heat sink compound.

A Word on Peltiers

There’s a lot of material around on what peltiers are and how they work, so I’m not going to bore you with more of that (Check out Cool Links; for bulding a peltier rig from scratch, go HERE.) Peltiers are marvelous devices for cooling CPUs below ambient temperatures – a real strong point. Peltiers have a number of weak points – they use a lot of power, they dump heat into a case like an oven and they can condense water out of the air like nothing you’ve ever seen before.

Power is easy to solve – use a second power supply. Heat from peltiers requires careful attention to case venting and air-flow – manageable. Condensation is the tricky one – it can be insidious and a CPU/board killer. Water can form in the most devious places – inside the Slot 1, on the back of the motherboard or on the back-side of a PPGA chip. Dealing with condensation is a pre-requisite for the successful use of peltiers.

Two techniques can be used to mitigate condensation: One, use gaskets and sealers to keep moist air away from cold surfaces, and Two, run the peltier at room temperature so moisture does not condense on cold surfaces. Let’s see how Tom’s Peltier Kits stack up.

Tom’s Alpha/Socket 7 Kit

Installing the peltier is fairly easy – the instructions are adequate and, if you look at what’s included, what goes where is pretty obvious. The kit includes and aluminum cold plate which could stand some lapping, but otherwise it’s OK. Mounting this completed assembly onto the socket will require some jujitsu with the Alpha clip, and I would suggest you develop an alternate mounting method. I used the peltier on my BP6 and was able to compare peltier and non-peltier temps side-by-side.

With an ambient temp of 21 C and the C366s at 550 MHz, the peltier CPU ran at 20 C at idle (NT 4) while the regular Alpha ran the chip at 36 C, both at 2.0 v. A 16 C difference is damn significant! I used CPU Mark to stress out the chips and temps went to 36 and 21 C. This is about the best you could ask for to beat condensation problems.

I then pulled the non-peltier CPU out to see how this temp affected performance. I was very pleased to see that I could now run the C366 at 594 MHz where before I could hold 572 MHz. I could post at 606 MHz and run CP Mark, but towards the end it failed, although no BSOD. Gratifying performance at 2.0 volts!

I then installed the “Turbo” switch. I have an inordinate fear of condensation, and I figure the best way to handle it is to install a switch that allows you to run the peltier at 5 and 12 volts (the red and black wires = 5 volts, the yellow and black = 12 volts). It’s just a double pole 3-way switch you can get at Radio Shack for about $2. At 5 volts, it will not cool as much and therefore will avoid the condensation problem. What I found was that at 5 volts, the peltier cooled the CPU to 28 C at 550 MHz, completely stable, about 5 C below temps I usually see running the Alpha without the peltier. Now this I like – you can run the peltier without any fear of condensation at 5 volts, then switch to “Turbo” when you run CPU intensive programs.

Tom’s Alpha/Celeron/PII/PIII/ Peltier Kit

The other kit, which fits on the large 2 fan Alpha, did not meet the room temp criteria (room temp = 22 C) under most conditions. I used this on the SOYO 6BA +IV with a C300a. The table below shows temps at 5 and 12 volts, with Waterfall running, without Waterfall and running Prime 95 at 450 MHz and 504 MHz.

Speed12 Volts12 Volts12 Volts5 Volts5 Volts5 Volts
 Restx-H2OP 95Restx-H2OP 95
450 MHz-15 C5 C9 C0 C18 C22 C
504 MHz-13 C9 C13 C1 C23 CNA

Rest = Idle with Waterfall, x-H2O = Idle without Waterfall, P 95 = Running Prime 95, NA = Unstable

This is impressive performance as this CPU does not run 504 stable without the peltier. However, make no mistake here – controlling condensation is the main task with these temps – Notice the 26 C swing in temps at 504! Tom’s kit has all the makings to do this, but it requires careful attention to detail. I also think the “Turbo” switch is absolutely required for safety’s sake and would not run this setup without it.

I measured temps at the back plate with the CPU at 0 C and found the back plate temp at 20 C. I also measured the CPU’s PCB at the base of the Slot 1 and it was 20 C also. At very high humidity, this can condense moisture with temps only a few degrees over this.

This kit is great for experimenting with peltiers and can lead to some impressive performance gains, but if you’re not actively monitoring temps while using this, you’re headed for trouble. With some additional measures to further isolate the back plate and Slot 1 from moisture, I think this could be a viable solution. For an “install it and leave it” approach, this is not going to do it.


Tom’s Alpha/Socket 7 Kit has incredible potential for PPGA cooling. Check out Wes’s BP6 @ 560 MHz for someone who used this kit very successfully on a BP6 with C366s. Using it with the “Turbo” switch and carefully monitoring CPU temps, this can be a viable everyday solution.

Tom’s Alpha/Celeron/PII/PIII kit is a more potent cooling solution with great potential also, but it also has more condensation issues than the Socket 7 kit. I think it is ideal for the overclocker who wants to explore peltiers and, with very careful attention to controlling condensation and using the “Turbo” switch, could be viable long-term cooling solution.

I again caution anyone thinking of using peltiers: These are double-edged swords. Great potential for CPU cooling, great potential to trash your CPU and motherboard. Your move.

We now have these in stock for $30 – more info HERE.)


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