Bitcoin Forum

So I finally got my 6990 setup running correctly under Ubuntu 11.04. Been doing some testing with the various settings, and so far with a single core running I'm able to hit just over 400MH/s. However, as soon as I enable the second core, both drop to more in the 340MH/s range. Is this to be expected with a dual GPU card like this? Are there any settings you'd suggest modifying to see if it makes a difference?

This does not happen under Windows 7. On all of my 6990's, all single GPUs are running at 405Mhash/s max. How is CPU usage/aggression level?

Also, you probably know but be sure to monitor GPU temps as they could be throttling.


I believe.

I can keep the aggression high since its a server that I don't need a responsive desktop on. Also, temps under load stay in the upper 70s to low 80s range, regardless of one or both cores going.

The one thing I did notice however, is that when I'm only mining with one core, GPU usage as displayed by aticonfig --odgc is a constant 99. However, mining on both cores results in usage on both to alternate between 100% and 0%.

Check your cpu usage. Is it pegged? Also, does the primary display run by itself get a steady hash rate as high as the secondary card run by itself?

There is some kind of issue with the ubuntu gui that causes cpu to max out when mining on the primary display, slowing down ALL gpus.

If you switch to headless it will go away.

Cpu usage should be < 10% if things are working properly.

CPU generally never jumps over a few percent. Either card, when run on it's own, is able to hit 400MH/s. Also, the setup is already headless.

what miner do you use and what flags do you use?
can you please paste the code?

Replied to your PM but will list summary here too.

The most important factor is bumping core clock up (mine is at 940) and using the switch on the top of the 6990's to use the unlock/super/kill the polar bears mode. Then phoenix with poclbm. The rest of the options just tweak to maximum performance.

Have you disabled Cross Fire?
When crossfire is enabled commands are sent to the 2nd GPU through the 1st GPU creating a bottleneck.

Currently mining using the following:

 ./poclbm.py  -d0 -w 128 -r 5 -f 0 -v
 ./poclbm.py  -d1 -w 128 -r 5 -f 0 -v

When the first one is launched it runs at 400MH/s until the second is launched at which device 0 levels off around 350 and d1 around 325. Crossfire is disabled. I've also tried an equivalent setup with phoenix using both the poclbm and phatk kernels. This one edges them out just slightly for my setup.

Well I'm pretty sure that's normal...mine does the same thing. Together it does 700mh/s so that is near the mining hardware comparison charts.

Have you increased the stock voltage?
The 6000 Series dynamically underclocks if there is a lack of power to prevent a crash.
In windows the catalyst control centre lets you up the voltage by 20%.

I haven't increased the voltage beyond the onboard switch being set to position 1. After some more experimentation thought, it seems to be heat related. When both are initially started, I can usually get a minute or so where they are running at ~400MH/s each. Then as the temp climbs and levels out in the low 80s, the hash rate drops a bit and settles. When I opened the case and got some additional fans going, if I can keep the temps in the mid to upper 70s under load, both cores are able to stick near 400MH/s. So with that in mind, any ideas for the most efficient way to improve cooling with this card? The case is a big with lots of room, and all cabling is routed on the back side of the motherboard. Currently has 3x200mm fans and a 140mm as well, so I think airflow inside the case is going to be to tough to improve. I suppose water cooling might be an option? I don't have a ton of experience water cooling, but I assume there are blocks available for the 6990 by now?

http://www.koolance.com/water-cooling/product_info.php?product_id=1117

Does the GPU fan (or fans) run at full speed? I found that (in Windows) my 6950 would happily go past 90C and the drivers wouldn't bother increasing the fan past 38%. Manually putting it up to 45% brought it down to 80C.

I did notice that leaving the fans on auto they typically never spun up past about 40%. I've gone to manually setting the speeds on them for the moment. I can keep the temps in the low 80s at 50-60% fan speed, and currently at 100% is where the temp is maxing out just about 80, but I'm getting somewhat better performance from the card as well. Currently I'm running in the 700-725MH/s range up from more like 650-675.