I have recently swapped my HD5850 from Collatz to Milkyway.

Running CPU-Z 0.4.2 showed the following -

When running Collatz the main GPU temperature was 78C, and the VDDC current draw was 26.5 A to 28.5A.

Running Milkyway has raised the GPU temperature to 81c to 82c, and the VDDC current draw to 45.3A.

The GPU load was steady at 95% for each.

I need to raise the percentage fan speed to cool the GPU slightly.

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Go away, I was asleep

What gpu memory clock setting are you using ?

Regards
Zy

Looks like around 1100-1150Mhz, if so, reduce it to around 500-550Mhz - Milkyway is not memory speed dependent, and all a high memory clock does is maintain a nice space heater.

Collatz needs high memory to cope with the high number of calculations it does, its the opposite for MW.

At 500-550Mhz for memory at MW you will save a bunch of power, and run a lot cooler.

Regards
Zy

What gpu memory clock setting are you using ?

Regards
Zy

Core clock 755 amd memory cloch 1125

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Go away, I was asleep

Collatz needs high memory to cope with the high number of calculations it does, its the opposite for MW.

Actually, Collatz uses far more lookups to large tables (16 MB in size, don't fit the caches) in the graphics card memory than Milkyway. Milkyway also uses lookup tables, but they are a lot smaller, are accessed less often and then even in regular patterns, which makes the caches of the GPUs very effective.
In contrast, with Collatz the GPU really has to read the values from memory in most cases (tables are larger than caches, virtually random access pattern). This makes it far more sensitive to the memory frequency/bandwidth (but it isn't solely limited by it) than Milkyway.

What gpu memory clock setting are you using ?
Regards
Zy

Core clock 755 amd memory cloch 1125

Drop the memory down to circa 500-550, there is no benefit at MW for a high memory setting (see CP's explanation above).

That, might, also give more room for a higher GPU clocks (I am unsure of the latter as I dont have a 5850, I dont know its max clocks)

Regards
Zy

The CCC Overdrive part allows me to drop the Memory Clock to a minimum of 900 MHz. I chose 10000, and also raised the fan percentage, on manual, to 75% (from 33%).

The GPU temperature is now a balmy 68c with a GPU load about 94% and no screen pulse.

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Go away, I was asleep

The GPU will happily purr along at 80 degrees. It will throttle itself incrementaly at 105 degrees, and the thermal cut out operates at 120 degrees. There is plenty of space there to drop the memory to the minimum you can get it, and lower the fan a little to settle at 80 degrees - less noise, less power draw.

Regards
Zy

My 4870 is happily running at 175mhz mem atm, with no impact on the project's speed. BTW, in order to drop below the CCC's limits you need to use something like ATI Tray tools with OC limits disabled.

The CCC Overdrive part allows me to drop the Memory Clock to a minimum of 900 MHz. I chose 10000, and also raised the fan percentage, on manual, to 75% (from 33%).

The GPU temperature is now a balmy 68c with a GPU load about 94% and no screen pulse.

As "heat is your enemy" has been drilled into me since day one of my OCing days, I run all my GPUs at 100% fan speed. This not only keeps the GPU cooler but all the surrounding components, it also means the air coming off the card is cooler.

Noise is not a problem from my 48xx series card fans and not from my HAF932 case fans.