Low Mhash/s with 2X 6950

[Islander92]

Hey Guys !

I'm new to bitcoin mining, but I started with this rig :

- 2X XFX ATI Radeon 6950 1Gb
- AMD Phenom II X6 Black Edition 1100T @ 3.5Ghz
- 1100W Power Supply
- 8Gb Mushin RAM @ 1333Mhz 

(Tell me if you need more infos)

I joined a pool (Deepbit.net), updated my drivers, installed GUIminer and I've setup my 2 miners (one for each card). I also changed my fan speed to 100%

But with all this I get 510Mhash/s... Wich is really crap for this setup. Can you guys help me with that ?

https://i.imgur.com/TJ0nI.png

[jake262144]

Obviously, once you got mining going now is the time for overclocking and fine-tuning.

Read those to get yourself up to speed:
GUI Miner thread
Hardware subforum

When in doubt, use the Search function && RTFM.
Report specific issues here.

Once you get familiarized with mining I suggest you switch to cgminer which is the most advanced miner currently available.
CGminer thread

If your machine is going to be used as a dedicated mining rig:
(1) Never use crossfire. Make sure the crossfire connector is removed.
(2) Don't overclock that CPU. You aren't going to need it. You might also opt to disable half of the cores - that will increase your power efficiency.
(3) There's no good explanation to stick with Windows.

[asdf2121]

temps... check it..

[juggalodarkclow]

Another issue is probably the fact that you're using the new drivers, I rolled back to catalyst 11.11 but here's another option to rollback to the previous sdk https://bitcointalk.org/index.php?topic=56885.0

Hope this helps

[grue]

whatever you do, don't join deepbit, or for that matter, any pool that is too big. it can compromise the security of the network, and they're the pool with the highest fees!

[luo demin]

-v -w128 -f30     use these flags for your 6950's and see what happens should be a significant improvement

[Costia]

-v -w128 -f30     use these flags for your 6950's and see what happens should be a significant improvement

+1 on this one
i have a 5770
without any flags i got 130Mhash/s
with -v -w 128 it jumped to 180

[naypalm]

-v -w128 -f30     use these flags for your 6950's and see what happens should be a significant improvement

poclbm rocks! I get ~330-350 out of each of mine.

[mmbregman]

-v -w128 -f30     use these flags for your 6950's and see what happens should be a significant improvement

-f30 is a defualt flag on the GUIMiner. To get the best Hash rate you should use -f1 (from my expirince on 6950), though it makes the desktop a little laggy.

[Costia]

I use -f 90 or 120 so i can play SWTOR even while i mine
The miner runs and the background and gets throttled by the "-f 90" when i play

[squirrelman]

I use -f 90 or 120 so i can play SWTOR even while i mine
The miner runs and the background and gets throttled by the "-f 90" when i play

Thanks for posting that, I will have to remember to use that when I want to game rather than just shutting down totally.