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A juggernaut at 90 degrees
Product : Alpha PEP66U
Price : 32.49 Including VAT
Available from : Overclockers UK
Related articles : [ThermoEngine Ultra]

If you are one of the many slot-to-socket users (like myself), then you'll know how hard it is to find a good heatsink/fan which doesn't take up a couple of DIMM slots. This is where Alpha's PEP66U steps in. A cooler specifically designed for slot-to- socket users in mind, it features Alpha's trademark copper base, among it's other traits.

The PEP66 has been around for quite sometime now, and Alpha have updated it and added "U" onto the end of it's name. Alpha built up it's good reputation in the days when full copper heatsinks were out of the question. When it was too expensive to make these copper juggernauts, they made heatsinks which were still aluminium, but went round the problem of cost by putting a copper inlay into the base of the heatsink. This was a good way of increasing the performance from the heatsink and still avoiding the cost of a full copper heatsink.

It worked well and one of their main models the PAL6035, which has been around for well over 16 months is still widely acclaimed. Alpha then introduced further models in their range, and we are going to take a look at their PEP66U. While it was designed for use in slot-to-socket environments, the white case can be turned around and it will serve as a normal cooler for use on Socket 370 and Socket A processors.

The PEP66U comes with a set of sponge spacers, which help it support itself and not put excessive pressure on the processor's core. This was a feature that was added to the "U" version of the heatsink. Older models did not feature the sponge feet, and this mainly grew out of people finding that early heatsinks on the Socket A circuit cracked their processors, due to putting excessive pressure on the core of the processor. Although now the stories are very few and far between, Alpha have included the "feet" as a precaution.


Installation requires a little assembly, although they are detailed in clear and concise steps on the instruction sheet that is provided. The first thing you notice when you take the heatsink out of the box is how large it is. The sink, coloured black is huge, and has long, thin fins sticking out of it's base. As you will see further down in the review, I took a comparison picture, putting it beside the recently reviewed ThermoEngine Ultra and it was even larger than that!

The white cover, which contains the holes for the fan screws has to be screwed into the heatsink itself. Screws are supplied and the operation shouldn't take more than 2 minutes for even the slowest of people. The retainer clip that is supplied is one that we have seen before in Alpha heatsinks, and generally speaking it works quite well. The two piece retainer clip, which has a rotational clip on one end does require quite a bit of pressure to attach, but once it is in place, there was a steady and firm contact between the heatsink and the processor core.

The heatsink doesn't come with a thermal pad, which is no bad thing, since most people just rip it off and put a thermal compound of their choice anyway. In our case, we stuck behind our Arctic Silver II (review here) and spread a thin layer of it.

From start to finish it took us less than 5 minutes to get the Alpha PEP66U on our Pentium 3 processor and we were ready to move onto testing.


To test the Alpha PEP66U we used our Pentium III 750MHz CPU which was overclocked to 933MHz. We compared the PEP66U against the stock Intel heatsink.

We were surprised with the fact that our Intel Stock heatsink/fan managed the haul to 933MHz. The PEP66U performed very well, and we were pleased to see that there was just over 2C difference between the temperatures during the 24 hour test period.

We probably could have pushed our Pentium 3 nearer the magic 1GHz barrier, but having reached 933MHz using the default 1.65v we were happy to leave it as it is.


The Alpha PEP66U is a very nice performer. It's designed for people that use slot-to-socket converters and don't want to loose all their DIMM slots in the search for a good heatsink. It's design is very good, and we managed to utilise all our DIMM slots (and with memory so cheap these days, who wouldn't?). The copper inlay on the base of the PEP66U is certainly a good way of avoiding high costs, but retaining some of the advantages of using copper as a material for thermal energy dissipation.

The PEP66U is a flexible heatsink. Even though it has been designed for slot-to-socket use, the white case can be unscrewed and turned around, so that the fan blows air directly on the base of the heatsink. It can cater for both Socket A and Socket 370 processors, and the heatsink is one of the biggest around. While it might not be able to keep up with the all copper heatsinks of today, it certainly provides good performance and flexibility.

As promised earlier, here is the picture of how the PEP66 compares, in size against the ThermoEngine Ultra and an old P166.