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Cooljag JAC311C-A
Product : Cooljag JAC311C-A
Price : ~7.00
Manufacturer : Cooljag
Supports : Intel Pentium 3 (Socket 370) up to 1.13Ghz and AMD Athlon 1700+

It's not often you get to see such a brilliant piece of engineering in such a small product coupled to such a price point but we were lucky enough to do so. When you are building rackmount servers you are in combat with two hard fighting, low hitting enemies. Space and heat. This isn't so much of a problem if you build systems that are greater than 4 Units (as a rough guide 1 unit is the height of a CDROM drive), however when you are in the 1 or 2 Unit configurations you need some serious kit to cool powerful computers down. If you still have no idea what these units are then here's the explanation.

In data-centres computers are stacked together in racks. This is done so that the greatest density of computers can be achieved (space costs money). In a 19" rack, you usually have 42units (this varies from place to place), but generally around 36 to 42 units per rack. The "thinner" your server is, the less rent you pay for the rackspace. 1 Unit is the height of a CDROM (roughly) and 2 Units are multiples of that. Now you can imagine what sort of lengths server builders go to when trying to fit a dual processor system in something that can't have anything taller than 1.75".

So, when we were building our new web server, which was a dual Pentium 3 1Ghz and it was being housed in a 1 unit case we had to source some really special heatsinks for the job. We found a Taiwanese based company called Cooljag and ordered a job lot of 10 JAC311C-A and a few weeks later we were presented with them. Considering we had paid under 7 per piece, the first impression of the heatsink was very good, but initial thoughts can always decieve.

Active low profile heatsinks are hard to produce. Due to the height restrictions it is almost impossible to balance the size of the heatsink with the size of a fan, however Cooljag have used a pure copper heatsink and gave it their skiving treatment. Then they placed a 24 CFM fan on top and we have the finished product. Skiving is a technique used to increase the surface area of the fins, which inturn translates to greater cooling efficiency. When you are talking about a heatsink that is only 11mm high you need all the surface are you can muster.

The heatsink is only one part of the problem. Airflow to cool the heatsink down is a serious issue and trying to squeeze a fan ontop a heatsink can be a little too much for most manufacturers. However Cooljag have managed it, with a purty 24 CFM unit. Not quite the 80 CFM Delta units you can buy, however it still produces the noise and allows there to be enough headroom in a 1 Unit case so that air can flow through the fan.

The unit itself is assembled from four parts. The heatsink, fan, mounting for the fan and the retainer clip. The heatsink's base is nicely polished and most people wouldn't bother sanding/polishing it further. For our tests we didn't. The base doesn't have a thermal compound pad fitted as standard, so we used Arctic Silver 3 in our tests.

We tested it in one of our 1 Unit machines, however the problem we had was not with the product itself, but comparing it to another product in this environment. However the specifications of the machine were as follows :-

  • Dual Intel Pentium 3 1Ghz
  • 1256Mb PC133 Crucial RAM
  • AOpen DX34-Plus motherboard
  • 1 80mm horizontal flow fan pushing cold air into the case

    The machine was put under full load - by that we mean the processor was being utilized 100% all the time (by running programs such as Seti, etc).




    Whilst it might seem the temperatures are quite high, you have to remember that air flow within a 1 Unit rackmount case is not the same as your normal case you have at home. The fact that we were able to perform these tests without the computer seizing up is a surprise. The reason why there is a temperature rise between 10 to 30 minutes is due to the change in temperature of the ambient air. It takes a while for the temperature of the air to stabilize. This is where most 1 Unit coolers fail - the heatsink doesn't get actively cooled.

    However we were still unable to compare it against another cooler, simply because there wasn't another cooler that would fit in the 1 Unit case. Some of you might be screaming out that there is a low profile Golden Orb that does fit into these cases, however we couldn't get hold of one and our experiance with Golden Orbs suggested they weren't very good at cooling processors which have high frequencies - they look nice though.

    In order to compare, we installed the JAC311C in a normal mini tower case (Coolermaster ATCS 201) and compared it against the Silver Mountain. Whilst it was pretty obvious from the outset the Silver Mountain will perform better in this situation (mainly due to increased surface area and fan power), it was surprising to see the JAC311C kept with the pace. We didn't bother overclocking the CPU since the JAC311C isn't made for that kind of application.

  • Single AMD Athlon 1.4Ghz
  • 512Mb Kingmax PC2100 TinyBGA DDR RAM
  • Abit K7RA-133 motherboard (thanks Overclock UK)
  • Coolermaster ATCS 201 case (4 80mm case fans - 2 intakes, 1 exhaust and 1 top mounted exhaust)





    These results surprised us a little. Whilst there isn't much surprise that the Silver Mountain offered better performance than the JAC311C, the difference in performance was smaller than we expected. The main reasons why the JAC311C was "under performing" were mainly due to the size of the fan it had. Whilst the Silver Mountain had a 7000RPM rated fan, shifting in the region of 36CFM, the JAC311C had a smaller 24.5CFM unit which spun along at 5300RPM. We were unable to fit the 7000RPM fan on the JAC311C, due to special screws it uses, however there is no doubt that if the fan was fitted then performance would increase.

    The other reason is surface area. However good Cooljag's skiving technology is, it won't be able to have the same surface area of a heatsink that is almost 4 times the height of the JAC311C. It came close though.

    So, what can we conclude about this heatsink? Well, it's one of the best made heatsinks we've seen. For the 7 we paid (per unit) the unit that was presented to us performed ahead of expectations and allowed us to even compare it against one of the previous greats in the Socket A market. If Cooljag produced a full size version of the JAC311C, using their skiving technology we would love to see how it performs.

    A great product from a relatively unknown name.