Topic: 5970 VRM Cooling Solutions (Read 7415 times)

i was refering to the copper strip...

How can you call that "done" when you bade it worse?

Last time i check human fingers arent flat; and to have the lapping done correctly, the sanding area must be larger than the base of the heatsink.

I cut some piece of sandpaper (about 3cm x 5cm) and was rubbing it around the heatsink gpu area with my finger . Yes, it was "smoothing" and I shouldn't do it this way because the resulting surface is not perfectly flat.

prably held it in his fingers and rubbed it back and forth on a sheet of sanding paper... while at the same time trying not to wear of his fingers.
it can be done... not as easily as lapping a CPU but it can be done.

How did you lap the strip? Dont tell me you scrubbed fine sandpaper on it. Lapping requires much for precise and it has to be done on completely flat surface. What you did was "smoothing" the base which does not give perfect flat.

I suspect you did the same with the heatsink. You just made it worse.

 

well thats it...
you will just have to buy another video card and start all over...
this has to be precise...

ps: in case it was missed... this was sarcasm

I checked my card temperature old logs and it seems, that I have exaggerated the gpu temperature increase, instead of 5 it was like 2-3 degrees C. Moreover, I noticed the increase some time after modification and the environment temperature changed so I am not precise here.

lapping the GPU core area could be a problem.
this change in thickness could be the reason for increates temperatures in the GPU.
perhaps you can apply more pressure to the GPU core to compensate.

my 6990 waterblocks has a problem with this in regards to contact with the VRM
I had to file off one of teh standoffs by a little bit to compensate.

Actually I have been lapping the copper plate with super fine sandpaper (P1000, P1500) to make it more smooth. Also the cutting of the strips could be quite problematic because they should be really flat.
Moreover, I lapped also gpu core radiator area, maybe I haven't done this properly and only worsened gpu core temps.

impossible, you have no grip

The gpu die has its own srews, so I think that the strips shouldn't lessen contact pressure significantly. But the elements located close to VRMs, like memory and CPLA-3-50( http://images.anandtech.com/reviews/video/ATI/5970OC/Card.jpg ) cooled with thermal pads could have significantly less contact. But those elements doesn't heat much during mining I believe.
I haven't done any precise measurement of the thickness, just estimated basing on the old, used VRM thermal pads (how much they were squeezed).

you could always try lapping the copper strip trimming a little bit off it.
not much but just a little and then see if your GPU temp drops a little bit.

That is also because the GPU die got less contact pressure or lack of contact due to the copper strip being too thick?
I dont know but i assumed you did use precision measurement of the thickness needed for VRM?

I have made some solution for cooling VRMs on my 5970. First, after opening the card I removed original VRM thermal pads, which fell apart and seemed dried.  I replaced them with some 1mm thick, 6W/mK thermal conductive pads from thermagon inc., but in result the VRM temps haven't improved.
Later I decided to experiment more and replace the thermal pads with copper plate and thermal grease.  I bought a 0.3mm thick copper plate and cut from it two strips to cover the VRM banks. I put nonconductive thermal grease (zm-stg2) on the surface of each VRM in the two banks and on the radiator side where VRM thermal pads had been previously stuck. Then, I carefully stuck the copper strips to the radiator side and put the card together. Results:
Pros:
- vrm temps dropped about 10-15 degrees C and stayed below 120 degrees C (threshold temp) even with high core voltage like 1.15V,
- overclocking capability increased significantly – voltage could be risen much higher compared to pads
Cons:
- gpu temps increased about five 2-3 degrees C, probably partly because of the better conductivity of heat from the vrm bank between gpu cores to the radiator which in result heats more when cooling gpus, but maybe also the original grease on gpus was better than my zm-stg2.
- I have read that producer uses thermal pads because during manufecturing the vrms could be soldered/placed at different hight and thermal pad could compensate this differences. It implies that the copper strip could not stick well to all vrms, or the one sticking out to much could get smashed maybe.
- quite risky - copper strip shouldn't touch any element...,  the pcb area close to vrms gets dirty with grease

Overall, I think that for bitcoin mining this modification could not be needed, because increasing voltage is not economical. And standard vrm cooling (with pads) is rather enough for economical (slight) oveclocking.

Remarks:
I also tried putting only thermal grease instead of pads and resulting vrm temps were better than with pads, so vrms are well tightened to radiator in my card at least.
The vrm bank with three vrms located between gpu cores heats more, in my card about 10 degrees C more, than the other bank (above fan), contrary to what this article says (I think, they misidentified the vrm banks): http://www.anandtech.com/show/3590 . But otherwise it's worth looking at, there are good pictures of the card.

If you open up the fins on the heat sink, your temps would drop a lot more.  Love the idea.

The VRM R5 should fit to cool that rear row of VRMs. For those 3 in the middle you would have to cook up something else. Either the baseplate, that you would have to cut to make room for the R5, and on which you can glue lots of sticky heatsinks, or something else.

Im not sure which VRMs do what on this card, but on a  5870 the rear row has all the VRMs that supply the GPU, and closer to the front of the GPU is a VRM that powers the RAM chips, and as a result doesnt get nearly as hot (still needs a heatsink, but a simple ram cooler with some hotglue or even zip tie works well enough). But if those 3 VRMs provide power to the second GPU, you will want something better than a tiny ziptied heatsink.

Edit: I see 3 banks. One large one, near that rules (6 VRMs), one with 3 in a row near the top, presumably for the second GPU, and I see a single one inbetween, also near the top, which I would guess is for the RAM.

Yup.  CFM =/= pressure.  You can have a high CFM fan with no pressure or a lower CFM fan w/ higher pressure.

If you did want to try w/ some 120mm fans you would want some 38mm thick Deltas designed for high air pressure situations.  It isn't going to be quiet though.

I don't think you will be able to get any decent flow with 120mm fans. They aren't pressure fans, so they will more than likely just spin in place instead of pushing air through the ducting. The reason they use those squirrel cage fans is because they can handle the backpressure of forcing air through that style of heatsink.

And that bank of VRM is actually 2 sets of VRM.  The smaller one provides power for the RAM (which runs at different voltage).  The other for GPU1.  The bank at top of the card provides power for GPU2.

This photo (link only because it is large) shows it more clearly.
http://lab501.ro/wp-content/uploads/2009/11/HD5970-Inside-09.JPG

The CPLA-3-50 and CPL-2-50 are inductors for VRMs.  The small squares next to each inductor are the VRM in that group.