Lapping a eVga G-FX 5900

Dak · 08-10-2004, 10:26 PM

I am building a gpu block to go along with the rest of my watercooling system. Today, I pulled off the heatsink to get a dry fit and found that the gpu was extremely convex. My guess is that I would only have a very little bit of contact in the very center.

I have two options: half a tube of AS and "low performance", or lap.

Does anyone have any idea how much material there is on the processor before I hit the core? All the threads and guides Ive seen are for GeForce4 era cards... Is it safe to assume nVidia hasn't changed their manufacturing processes?

killernoodle · 08-11-2004, 01:36 AM

Dont worry if it is convex, worry if it is concave

Anyways, how did you measure the level of concavity?

Dak · 08-11-2004, 12:30 PM

Quote:

Originally Posted by killernoodle

Dont worry if it is convex, worry if it is concave

Anyways, how did you measure the level of concavity?

It's crazy convex. I'll see if I can produce a picture. It reminds me of a contact lens.

As far as "measure the level of concavity", I didn't not measure the level, per se, but i verified it with a machinist's straightedge. It's certainly not flat.

Butcher · 08-11-2004, 12:41 PM

Hmm, I assumed FX5900 chips were flip-chips like 9800 pros, guess not...

killernoodle · 08-11-2004, 12:48 PM

Do you know the difference between concave and convex?

Think Concave as a Cave. It dips in with high points along the edge.
Convex is higher in the middle than on the edges and is much more desireable with cores because there would be better heat transfer over the core.

Either way it shouldnt matter that much unless the difference was astromomical. You can always re-shape the heatsink/waterblock to fit the graphics card because I imagine lapping the GPU would be tough to do right.

Dak · 08-11-2004, 01:44 PM

Quote:

Originally Posted by killernoodle

Do you know the difference between concave and convex?

Think Concave as a Cave. It dips in with high points along the edge.
Convex is higher in the middle than on the edges and is much more desireable with cores because there would be better heat transfer over the core.

I do my best not to swallow my tongue.

YES I KNOW. ITS CONVEX. It has a high center.

How hot is too hot for a GPU? I put a ton of AS on it and put the stock HS back on it, and its running ~110(C) according to the nvidia utility.

Dak · 08-11-2004, 03:53 PM

Went home during lunch, and verified my previous measurements...

You'll have to bear with this, my father is the mechanic, I'm merely a noob who enjoys milling:

placed the straight edge on the gpu gently. Took out his feeler gauges that he uses for checking heads for flush-ness. Switched to the largest available feeler. I was able to slide this under both sides of the straight edge. The gpu is not flat, and it is certainly convex.

If its worth polishing cpu blocks til they are mirror like, why would i settle for only 1/16 of the top of the waterblock to contact with my gpu? I don't think its an option to reshape the gpu block. The chances of me getting them to mate good is just about nil, and there isn't a whole lot of material left on the bottom (made the bottom plate as thin as I thought was reasonable.)

I have always been told that very minute scratches on a cpu block reduce performance... I can't imagine a 1/32nd gap is acceptable

So... Does anyone know how much material I have to play with?

Dak · 08-12-2004, 01:28 AM

partially lapped it. Have a flatish center spot about the size of a nickel. Dropped my temps ~10C.

Will probably lap more when i reinstall my watercooling. Thank you for the input.

Butcher · 08-12-2004, 04:45 AM

Quote:

Originally Posted by Dak

How hot is too hot for a GPU? I put a ton of AS on it and put the stock HS back on it, and its running ~110(C) according to the nvidia utility.

Should be below 60C ish....

fafnir · 08-18-2004, 08:45 PM

instead of lapping the chip, there is a metal cover or heatspreader on top; a thin sheet of metal, which is not flat, which you can remove by ripping it off with cutters by gripping one of the edges

look on the side of the chip and you will understand what you have to tear off

perfectly safe assuming you see what you have to do

_

AngryAlpaca · 08-18-2004, 09:23 PM

50lbs of force + one convex GPU = one flat GPU.

Butcher · 08-19-2004, 05:04 AM

Quote:

Originally Posted by AngryAlpaca

50lbs of force + one convex GPU = one flat GPU.

Or one broken gpu.

AngryAlpaca · 08-19-2004, 09:03 AM

I was really making a random guess at the mounting force. It, like a convex heat spreader on a CPU, probably flattens out with the recommended mounting force. I think this is a case of a DIYer knowing more than nVidia.

Dak · 08-19-2004, 04:01 PM

Is it possible to just tear the heatspreader off? That would make my life easier. I have a pretty shitty block design, but I bet it will be sufficient to just cool the core.

Dak · 08-24-2004, 06:33 AM

Whew, it was a pita, but I think I have it solved.

Some background: when I took the original heatsink off for the first time to dry fit my block, I used a pair of sissors to pry on it. Bad choice. I cut across a couple traces, although luckly /most/ of them weren't too bad. One of the "fingers" that reach into the agp slot was totally severed, however. Luckily I folded it back itno place, and things seemed to be working fine...

Tonight, I decide to lower my temps a bit, so i took my watercooling block off, and lapped it some. Got about 90% of it niiice and smooth, and decided that was good enough (a few of the low spots were /very/ low, I figured it was unimportant because they were around the edge). Put everything back together, and tried to boot.

No go. Apparently my shinanigans with the sissors had finally caught up with me. I showed my dad what was up with it, and he /rubbed it/. That totally f**ked me over. The little piece of metal was gone! I had a significant gap between the new end of the finger and where the trace started. GRR. In frustration (I figured I had a dead card anyways) I followed this pages advice and removed the heatspreader:
http://www.xbitlabs.com/articles/vid...modding_5.html
It came right off according to their instructions. Not hard at all!

After taking some pent up aggression out on the heatspreader, I got my soldering iron out and just soldered it back together. It looks like ass, and it probably doesn't have as good a connection, but oh well. It started working again

Plus, the temps are much much better. I know a lot of people in this forums poohpooh rambling off temps, but here we go:

Before I started screwing with it: No idea. Didn't know there was a screen in the driver window to check it

After I removed the stock heatsink and replaced pink cement with AS: 110C
After I lapped about 20% surface air, on stock heatsink: 100C
After I put on watercooling: 73C
After I lost it on the heatspreader: 36C

In theory the further lapping that went to waste would have probably got me near the 36ish mark. Only down side is that this modification brings my cpu temperature up because the VC is finally dumping some heat into the water

Thanks for the help guys.

08-10-2004, 10:26 PM	#1
Dak Cooling Neophyte Join Date: Aug 2004 Location: Alaska Posts: 15	Lapping a eVga G-FX 5900 I am building a gpu block to go along with the rest of my watercooling system. Today, I pulled off the heatsink to get a dry fit and found that the gpu was extremely convex. My guess is that I would only have a very little bit of contact in the very center. I have two options: half a tube of AS and "low performance", or lap. Does anyone have any idea how much material there is on the processor before I hit the core? All the threads and guides Ive seen are for GeForce4 era cards... Is it safe to assume nVidia hasn't changed their manufacturing processes?

08-11-2004, 01:36 AM	#2
killernoodle Thermophile Join Date: Sep 2002 Location: Charlotte, NC Posts: 1,014	Dont worry if it is convex, worry if it is concave Anyways, how did you measure the level of concavity? __________________ I have a nice computer.

08-11-2004, 12:41 PM	#4
Butcher Thermophile Join Date: May 2001 Location: UK Posts: 1,064	Hmm, I assumed FX5900 chips were flip-chips like 9800 pros, guess not... __________________ Once upon a time, in a land far far away...

08-11-2004, 12:48 PM	#5
killernoodle Thermophile Join Date: Sep 2002 Location: Charlotte, NC Posts: 1,014	Do you know the difference between concave and convex? Think Concave as a Cave. It dips in with high points along the edge. Convex is higher in the middle than on the edges and is much more desireable with cores because there would be better heat transfer over the core. Either way it shouldnt matter that much unless the difference was astromomical. You can always re-shape the heatsink/waterblock to fit the graphics card because I imagine lapping the GPU would be tough to do right. __________________ I have a nice computer.

08-19-2004, 09:03 AM	#13
AngryAlpaca Cooling Savant Join Date: Jan 2004 Location: Alberta Posts: 631	I was really making a random guess at the mounting force. It, like a convex heat spreader on a CPU, probably flattens out with the recommended mounting force. I think this is a case of a DIYer knowing more than nVidia. Last edited by AngryAlpaca; 08-19-2004 at 09:15 AM.

08-11-2004, 03:53 PM	#7
Dak Cooling Neophyte Join Date: Aug 2004 Location: Alaska Posts: 15	Went home during lunch, and verified my previous measurements... You'll have to bear with this, my father is the mechanic, I'm merely a noob who enjoys milling: placed the straight edge on the gpu gently. Took out his feeler gauges that he uses for checking heads for flush-ness. Switched to the largest available feeler. I was able to slide this under both sides of the straight edge. The gpu is not flat, and it is certainly convex. If its worth polishing cpu blocks til they are mirror like, why would i settle for only 1/16 of the top of the waterblock to contact with my gpu? I don't think its an option to reshape the gpu block. The chances of me getting them to mate good is just about nil, and there isn't a whole lot of material left on the bottom (made the bottom plate as thin as I thought was reasonable.) I have always been told that very minute scratches on a cpu block reduce performance... I can't imagine a 1/32nd gap is acceptable So... Does anyone know how much material I have to play with?

08-12-2004, 01:28 AM	#8
Dak Cooling Neophyte Join Date: Aug 2004 Location: Alaska Posts: 15	partially lapped it. Have a flatish center spot about the size of a nickel. Dropped my temps ~10C. Will probably lap more when i reinstall my watercooling. Thank you for the input.

08-18-2004, 08:45 PM	#10
fafnir Cooling Neophyte Join Date: Aug 2004 Location: moved Posts: 2	instead of lapping the chip, there is a metal cover or heatspreader on top; a thin sheet of metal, which is not flat, which you can remove by ripping it off with cutters by gripping one of the edges look on the side of the chip and you will understand what you have to tear off perfectly safe assuming you see what you have to do _

08-18-2004, 09:23 PM	#11
AngryAlpaca Cooling Savant Join Date: Jan 2004 Location: Alberta Posts: 631	50lbs of force + one convex GPU = one flat GPU.

08-19-2004, 04:01 PM	#14
Dak Cooling Neophyte Join Date: Aug 2004 Location: Alaska Posts: 15	Is it possible to just tear the heatspreader off? That would make my life easier. I have a pretty shitty block design, but I bet it will be sufficient to just cool the core.

08-24-2004, 06:33 AM	#15
Dak Cooling Neophyte Join Date: Aug 2004 Location: Alaska Posts: 15	Solution! Whew, it was a pita, but I think I have it solved. Some background: when I took the original heatsink off for the first time to dry fit my block, I used a pair of sissors to pry on it. Bad choice. I cut across a couple traces, although luckly /most/ of them weren't too bad. One of the "fingers" that reach into the agp slot was totally severed, however. Luckily I folded it back itno place, and things seemed to be working fine... Tonight, I decide to lower my temps a bit, so i took my watercooling block off, and lapped it some. Got about 90% of it niiice and smooth, and decided that was good enough (a few of the low spots were /very/ low, I figured it was unimportant because they were around the edge). Put everything back together, and tried to boot. No go. Apparently my shinanigans with the sissors had finally caught up with me. I showed my dad what was up with it, and he /rubbed it/. That totally fked me over. The little piece of metal was gone! I had a significant gap between the new end of the finger and where the trace started. GRR. In frustration (I figured I had a dead card anyways) I followed this pages advice and removed the heatspreader: http://www.xbitlabs.com/articles/vid...modding_5.html It came right off according to their instructions. Not hard at all! After taking some pent up aggression out on the heatspreader, I got my soldering iron out and just soldered it back together. It looks like ass, and it probably doesn't have as good a connection, but oh well. It started working again Plus, the temps are much much better. I know a lot of people in this forums poohpooh rambling off temps, but here we go: Before I started screwing with it: No idea. Didn't know there was a screen in the driver window to check it After I removed the stock heatsink and replaced pink cement with AS: 110C After I lapped about 20% surface air, on stock heatsink: 100C After I put on watercooling: 73C After I lost it on the heatspreader:** 36C In theory the further lapping that went to waste would have probably got me near the 36ish mark. Only down side is that this modification brings my cpu temperature up because the VC is finally dumping some heat into the water Thanks for the help guys.

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