4870 problems

[adrichardson]

Hi guys.

I recently bought a Musashi for my 4870 (the stock cooler is far too noisy for me).

I installed it last night, and all seemed well on the desktop (idle temps were a lot lower, no artifacting etc). I cranked up Furmark to test it, and it crashed after about 30 seconds (core load temp was much lower than with the stock cooler). I rebooted and ran the test again. Needless to say, it crashed, but this time I checked the VRM temperatures. All 3 VRM readings shot up to about 140c before it locked and crashed (in under a minute).

I installed the heatsinks on both sets of chips towards the back of the card as shown in the manual (I'm assuming these are the only VRM chips). I used a larger sink on the set of 2, and the longer, thin heatsink on the set of 3 chips. In hindsight there's no way that little sink could cope with temperatures that high...

I reinstalled the red plate from the stock cooler, and it was at least stable under full load. The VRMs hit around 118c after about 6 minutes. Definitely better, but still on the high end. I'm not particularly happy about using the stock heat plate to cool the VRMs and memory, but it's the best I can do at the moment. Any idea where I've screwed up? Also, is it worth adding sinks to the big chips in front of the VRMs? They're right under the fan on the stock cooler, so presumably they would benefit from better cooling.

Any help would be very much appreciated!

Cheers.

[sumo]

Hi adrichardson,

we knew about this "problem" with furmark and we are in contact with AMD about that. The point is that furmark disables the dynamic regulation from the VRMs, so its like you drive a car always in the first gear. In normal games you never reach such temperature levels and loads. We also test it in our lab and got something between 110-120°C (same heatsinks you choose), all run stable.

At which speed level you run the fans? Did you try it at full speed > also unstable?

Kind Regards
Chris

[adrichardson]

Hi Chris,

The fans were running on high (you can barely hear them on high, so I left them cranked right up).

I reinstalled the Scythe ram sinks last night, and ran rthdribl to stress test it (still very stressful if you force 16xAA @ 1680x1080). Under full load they peak at appx 83/88/88. Definitely much less worrying!

It might be worth stickying the Furmark issue - it's getting quite popular for stress testing these days.

I did notice that the VRMs were about 10c hotter with the Scythe sinks than they were with the heatplate from the stock cooler. Is beefier cooling for them recommended for overclocking?

I'm tempted to go for something like this if necessary:
Chilled PC UK - Watercooling made easy, The UKs Largest Selection of Watercooling

Cheers!