Cooljag JAC313C GPU Heatsink Modification

If you have read my Tweakmonster RAMsink guide, or checked out the Cooljag JAC304C Prelim, then you will know that I'm on a mad mission to freeze my MSI GeForce4 TI-4600. Before we review the performance of the JAC304C, I decided to review the 313C so I have something to base my results off.

The Cooljag JAC313C is invariably the most popular 1U cooler for GeForce4 cards. You can find them for sale all over the 'Net; I got this particular unit from Newegg.com. It's a great looking heatsink, and I've heard nothing but good things about it. Until I get to see the numbers, though, it's just hearsay ;-).

First we will check out the specs of this unit.

The 313C is extremely similar to the 304C - in fact, about the only difference is in the size of the heatsink. The 304C is about 7mm taller, and 21 grams heavier. Still, at 252 grams, this is undoubtebly a lot heavier than the stock heatsink on most GeForce4 cards. Because of this, and the application design of the heatsink, we will need high grade adhesive compound to keep the heatsink on the GPU. I will recommend Arctic Silver Thermal Adhesive as it is a high quality product that worked great on my Tweakmosnters.

Before we get started, let's look at the materials we will need for the installation:

• NVidia GeForce4 TI-4600 based video card
• Cooljag JAC313C
• Arctic Silver Thermal Adhesive
• Arctic Silver Thermal Compound
• Cotton Swabs (Q-Tips)
• 91% Isopropyl Alcohol
• Razor blade
• Pliers

At a minimum you will need AS Adhesive Compound to affix the heatsink to the GPU on your GF4. Realize, however, that once it dries it is not coming off! Since I plan on removing the JAC313C relatively soon in order to test the JAC304C, I need to be able to remove it eventually. I used Arctic Silver 3 Thermal Compound mixed in with the thermal adhesive to achieve this. The exact amount will be covered later, but if you want the option of removing your heatsink, pick up some AS3 before we get started.

The first step is getting the stock heatsink off the card. The GF4 has a spring loaded clip that makes it relatively easy to remove, although a bit strange if you haven't used one before. Referring to the pictures below, you will notice pin mounts on the two opposite corners of the HSF. You should be able to use a pair of pliers to remove them, I found a twist/pull motion to get them off pretty easily.

Once the pins have been removed, two plastic mounts should still be holding the heatsink on the card. Press firmly on the mounts from the underside of the card. You might have to pinch them through with a pair of needle nosed pliers. Once the mounts are free the heatsink should come off easily.

With the heatsink removed, it's time to clean the GPU off. The residue left behind should be completely removed before applying the AS adhesive or thermal compound. It isn't as easy as I might make it sound, but with a little patience and the right tools you should be able to remove all of the old thermal goo from the GPU.

I started off by thoroughly dousing the GPU in 91% isopropyl alcohol, and using a cotton swap to start loosening up the goop. After working at this for about 10 minutes, I used a razor blade and my 'helping hands' to scrape the residue. This works really well, but only use a blade if you are confident that you aren't going to scratch the face of your GPU. It's a delicate surface and you have to pay extremely close attention to your work.

You can use some kind of carb cleaner if you want, but no matter what you use, make sure it includes no oils, has very low acidity and especially isn't citrus based. Goo gone would have stripped this thing clean, I'm sure, but is very corrosive to electronics. Let's have a look at the processs:

Before we start glueing everything, stop for one minute and make sure you have all of your materials together. Once you start mixing the adhesive you will only have a few minutes to work with it, before the mixture heats up and begins hardening. Once the adhesive reaches a gel consistency it is unusable. Ensure that you have a place to mix your adhesive (anything will work as long as it's clean and flat, just use non-plastics).

This is where the Arctic Silver 3 thermal compound will become useful. Put a glob on the top of the heatsink, not much but enough to cover the heatsink in paste once spread. Now use sterile rubber gloves or a plastic bag to rub the compound into the heatsink. Rub the compound in circular motion until the entire face of the heatsink is covered. Now grab a paper towel or soft cloth and wipe it all off again. You will notice the HS has a slight tint to it now; this is a good thing, as it means the AS3 is filling in all the tiny hills and valleys.

Now that the heatsink is prepared, we are ready to mix our adhesive and install the sink. If you DON'T plan on removing the heatsink once installed, mix up a 1:1 combination of the Arctic Silver Adhesive Compound #1 and #2. If you DO plan on removing the heatsink, mix the AS adhesive normally, but the final mixture should be about 60% adhesive and 40% regular thermal compound. Mix everything before application, and then you can apply the mixture. Looking at the picture below you can see how much I used for my adhesive/compound mixture.

Place a small glob of the mixture on one corner of the GPU, and spread it evenly across the entire surface of the chip. The thickness you need will depend on your heatsink; for a properly lapped heatsink, a very thin layer will work fine. If your heatsink surface is less smooth, you will want a little more to ensure it makes full contact.

Again, you only have a few minutes to properly apply the adhesive. Be quick but precise, and if you feel like you are just making a mess, clean it up entirely with some isopropyl alcohol, and start over with a fresh batch. It's better to waste a little then have the adhesive harden all over your card, or in big clumps for example.

If everything goes well, you should be ready to install the heatsink on your GPU at this point. Referring to the pictures below, you want to line up the HS so the indented edge is facing toward the front of your case (i.e. away from the video jacks). Center the heatsink over the GPU and press it firmly down. It will take about 10-15 minutes to form a reasonably good bond between the HSF and GPU, so don't move the heatsink at all during this time. You may apply some pressure to help it make contact, but be careful not to twist the heatsink in either direction. Direct force on the center of the heatsink is appropriate.

And that's it! Now you want to wait at least two hours for the compound to harden. Don't use the card before this two hours is up, the last thing you need is that heatsink falling off during use. Once it's dry, throw it in your case and it's time to OC that sucker!

For all intents and purposes, this procedure is for overclockers. Unless you just want to make your card pretty (which is nice, too), installing a 1U HSF onto your video card is only done to squeeze a few more MHz out of your core OC. As such, I was extremely excited to finally test this unit out.

Although I won't share too many details, so as not to ruin the JAC313C vs. JAC304C review, I could have been happier with the results. In order to find the highest core OC possible, I ran benchmarks in 3dMark2001 SE, CodeCreatures (full bench), GLExcess (1024x768, all tests) and Novalogic's Comanche 4 demo bench. If it doesn't make it through every one of these tests, it isn't considered stable enough for a notable OC.

The highest OC I was able to run all of the benchmarks at with the stock cooler was 324.0MHz. Although I was able to run nearly everything at 333MHz with the JAC313C, it locked up during the CodeCreatures test. The highest stable clock I could hit with the JAC313C was 328.5MHz. A 4.5MHz jump. Not that impressive. However, there are some things to consider before jumping to any conclusions...

First of all, benchmarks were run about 4 hours after the 313C was installed. AS3 can take a few days of steady use before it reaches optimal temperatures. Given a few days to work its way in, may yield a few more MHz in the long run. Also, this card is at stock voltage. I plan on doing a voltage mod very soon, before the 304C test, so we will eliminate all possible restraining factors.

One thing of interest that I should mention before I say goodbye though, were my 3DMark scores. Although the other benchmarks didn't show such a major improvement from the additional 4.5MHz, 3DMark jumped from 11596 points at 324MHz core, to 11703MHz at 328.5 core. Not a huge jump, but in the past a few extra MHz would usually result in a another 30 or so points, not the 107 points like in this these tests. Hopefully this means that heat is not an issue, and the voltage is in fact holding this card back from a higher OC. Instead of gasping for air at 324.0MHz, the card may have been cool running at 328.5, but starving for voltage.

Well, I don't want to say too much. Take these benchmarks with a grain of salt. I'll have a full comparison focusing only on the benchmarks once the VMOD is finished and I have tested the JAC304C. Until then tweakers, may the hertz be with you!

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