Project Geforce 3 Cool down!

[amdkt7]

Ok, this has been a fun little project! Just reuse a few old parts and reap nice rewards! How does 5 degrees C cooler sound? Well, I hoped for more, but it's still good.

I had been thinking about replacing the HSF on my Visiontek Gf3 for more cooling, but I did not know just what to buy. I don't like orb style heatsinks, I don't think they have enough fin surface area. Well, yesterday morning I had shut down my computer and then restarted it, when the Visiontek fan began growling and had trouble spinning up. OK, lets see what I have laying around that I could replace it with...

First, I found out how easy it is to fix the fan, just peel the sticker off and spray a little "TV Tuner Spray" in to the bearing. Then wipe off the overspray and reseal with the lable or a piece of tape. The fan can be removed from the heatsink by gently prying it loose, it snaps back in.

I wanted something better though, I rumaged through my junk and found several HSFs. I considered a unit that came with my XP, the retail version, but decided it was too big and heavy, then I found a old HSF from an K6-2 system, it was a small thing from a 100-200 MHZ system. It looked like it would fit.

Now, how do I mount this thing? The clip sure would not work, so I removed it. It was not large enough to use the push pin holes, but there were four smaller holes closer to the chip. After a long search through my extensive collection of nuts, bolts and screws I finally found some tiny course threaded screws that would reach into the heatsink. I drilled two small holes into the heatsink, then lapped the heatsink to smooth it out and flatten the concave surface.

I applied thermal compond, expermented with ASII then settled on regular paste as the surface of the chip was rather concave as well. I had to experiment to find the right amount of paste to fill the gap in the middle of the chip and still have a thin layer on the edges as well.

I screwed the HSF on to the board, then mounted the fan. I did not like the original fan very well, so I went sorting through my fan collection again. Found my original Taisol fan, and liked that idea. 32 CFM, and fairly quite. Also it was oversized and when mounted on the heatsink it could also blow on the memory heatsinks. I'm posting pics to show what it looks like.

Securing the fan was a problem, one screw fit in the heatsink nicely, but one screw would not be enough. I had a brainstorm and slipped a bolt through the opposite corner and used a tiewrap. It worked great!

Next came testing. I used my Radio Shack IR thermometer to measure the temp of the backside of the circuit board, right where the ic is mounted. It's a little tricky, but I got repeatable results. BTW, its a non-contact thermeter, works using infared to measure surface temps. Instant readings, great fun to play with.

I found a 5C difference between the original hsf and my new rig, plus 2 to 3C lower memory temps.

I placed a temp probe on the board for monitoring (see the pic)and closed everything up.

[amdkt7]

This pic showes the board mounted and shows the side view of the heat sink and the cable tie holding the fan.

[amdkt7]

Next this pic shows the temp probe taped to the board. You can see the screws holding the hsf to the board.

Also note the massive passive heatsink on the northbridge chip above the video card..

[amdkt7]

This pic shows the instruments used to take temp readings.. the IR thermometer is not reading anything, just demonstating. The right meter is indicating the video card temp while overclocked. I don't think it reads the correct temp at all, but it is good for comparision readings.

I got readings of 45C with the IR probe, 37C with the standard probe taped to the board.

It seems that I should be able to get much lower temps than that, but I think that the air is getting trapped under the video card. My final temps should be lower as my side mounted case fans blow fresh air onto the video card. I may want to put a stronger fan in the side, but I like the quiet..

Why don't you lap the GPU? It'll make better contact with the HSF you put on it. You could use AS epoxy to fasten the HSF to the GPU.

When I did my GF2MX400, I epoxied an orb to the chip which I lapped and used Arctic Alumina epoxy to attach a small heatsink from a 486 to the backside of the card. Arctic Alumina is completely non-conductive. I did my Voodoo 5 5500 in the same way.

You can safely lap a GPU. They all seem concave to me. If you look closely at it, you will see little circles near a couple of the corners. I used those as a reference as to how far I could go in the interest of getting my GPUs flat.

[amdkt7]

How do you lap an GPU? I guess I would glue some sandpaper to something small and flat. There is not a lot of room there.

I'm scared to touch my video card with sandpaper!

I guess that it could help a lot and it should be safe as the ic casing is thick, the dust created by sanding is non-conductive and can be blown off the board.... I'm tempted to try it, I'm trying to think of a good way to do it though.

You described it pretty well. The trick is to sand it flat and level, so the HSF doesn't look cocked. In my experience, the IC is thick. You can look at the writing on the chip to see exactly how out of level the GPU is as you sand. I started mine with some 180 grit (yes, there was that much meat), worked into 320 grit and finished it with 600 grit. 600 grit makes it look like an unsanded surface. I removed the dust as I went along (didn't want it getting in the wrong places) and cleaned up the card with acetone and alcohol. I used the acetone as a final rinse.

I was pretty comfortable doing mine as I had a few video cards laying around in case it didn't work out well for me, but if you aren't comfortable with it, don't do it. I'd feel really bad if you lost your GF3. I have a GF4, but didn't do it to that. The stock HSF looks like it's doing a good job, but I would be lying if I didn't tell you I wasn't a little leary of sanding a $300 video card.

[amdkt7]

I'm wondering how much difference it would make for cooling the GPU. So many times I have tried things and had no detectable results. I think I might try it anyway just to see. I have been having video related problems that make me suspect the card anyway. If it dies it dies...

I think that I can safely do it anyway if I'm carefull.

Well, as I'm not an 1337 overclocker or anything, I can't really say. I can tell you that in my overclocking experience my GeForce 2 MX was always limited by the motherboard it's plugged into. It runs at a stock 200 mhz core and I've had it running at 240. It doesn't help me O/Cing the core, being what it is.

[amdkt7]

No, I don't care to overclock extreemly, I'm more concerned with cooling.

I do overclock when I'm playing Rally Throphy, but I stay with in the normal overclocking range as it gives me enough to play smoothly. I do wonder if card cooling is the reason for some of my graphics problems.