Overclock XFX HD6850 Black edition

[Guest yvansoftware]

Hi,

 

First of all, I do not need the card for gaming, but for pure OpenCL performance. I'm running XP, with all accelerated OS functions disabled, and the settings on "high performance", meaning that the taskbar and windows are not skinned, no effects on menus,...

 

I had bought a HD5770 for this, but it was a DoA. It survived 5 days under the heavy load, no overclock, but temp was waaaay to high (about 80-85°C) at 90-95% GPU usage. I returned it, there was no visible damage, but they couldn't deliver another 5770. The store decided to give me a XFX HD6850 Black Edition, and I payed a difference of about €20.

 

Now with this card, I get temps of 66°C to 70°C, which seems normal to me at full load. But the card does perform more than 15% less than the HD5770.

 

Since I read that this card can be overclocked relatively safe, I'm asking how and what settings to use. On what do I need to concentrate?

 

As I said, it will not be used for gaming, but for OpenCL calculations (I don't know if I'm allowed to talk about that system here. It's not (yet) illegal, and I'm trying to make the most out of it before it gets illegal ;-), and since we in Belgium have no government for over a year now, new laws are not written easily :-P ).

 

I have an older mainboard (PCI-e 16x 1.0a), but the HD5770 performed 15% better on the same slot, so I do not think this will be a serious bottleneck in my setup.

These are the specs:

• AMD Athlon64 4000+ (no X2)
  
• MSI K8N Neo4 Platinum mainboard
  
• 2GB DDR400
  
• 550W PSU
  

No CD/DVD drive and HDD to save power, the system boots of a 8GB CompactFlash card inserted into a PATA to CF adapter. (kind of a cheap butt solid state drive effect)

 

What tool do I need to use for the overclock? I have the latest Catalyst, and the latest APP SDKs.

Do I need to flash the card for optimal performance?

Where should I start with the frequencies?

 

I read that other users of this card using the same software overclocked the CPU of the card, and underclocked the RAM. Is this the way to go for pure OpenCL sha256 hashing, or do you guys recommend something else.

 

There is enough cooling in the case (3 case vents, a quite huge Zalman on the CPU, and the stock XFX on the GPU), and there are extra holes near the vents to optimize air stream.

 

One more thing, which is quite obvious: I do not want to blow the card :-P.

 

Thanks,

Yvan

[Black64]

With the temps you had on that 5770 there is no way your case has enough cooling. Vents are not the same has fans, you need serious(fan) airflow to keep a GPU that's under full load cool and stable. I would do that first to prevent it from failing like the 5770.

 

Second do not overclock that card if the temps are high, which they are. But it's your call.

 

Third to overclock the card go into CCC(Catalyst control center) and use overdrive. It's that easy.

Edited June 9, 2011 by Black6464

[imm0rt41]

One thing I was thinking could cause that 15% drop in performance despite the 6850 being newer, better, faster is that it could be bottlenecked by your CPU/mobo/RAM. Not really sure how to find out though lol

[Guest yvansoftware]

One thing I was thinking could cause that 15% drop in performance despite the 6850 being newer, better, faster is that it could be bottlenecked by your CPU/mobo/RAM. Not really sure how to find out though lol

 

 

The only factor that changed is the GPU... So I don't think that's the problem?

[IVIYTH0S]

The 6850 shouldn't be 15% slower, it should be 15% fasterif anything. Are you running the 11.5 drivers??

[imm0rt41]

The only factor that changed is the GPU... So I don't think that's the problem?

That's just it. Older CPUs and such (especially your single core) could have some problems pushing the data this card is looking for. My DDR2 memory severely limits my CPU OC, and therefore my GPU OC suffers when it is up near it's max. I noticed scores about 5% lower than what was expected for the card/cpu combo. I expect that to get a little better once I get a DDR3 mobo in my hands haha

[Guest yvansoftware]

That's just it. Older CPUs and such (especially your single core) could have some problems pushing the data this card is looking for. My DDR2 memory severely limits my CPU OC, and therefore my GPU OC suffers when it is up near it's max. I noticed scores about 5% lower than what was expected for the card/cpu combo. I expect that to get a little better once I get a DDR3 mobo in my hands haha

 

Actually, I solved the problem. The problem lied in the following "error": The software I was running through OpenCL on the GPU was not optimized for APP SDK 2.4, and on the support forums prestation losses of at least 10% are noticed. So I switched to an application with another OpenCL module, which properly supprted the APP SDK 2.4. This card is not overclocked at all now, and I see a performance increase of about 27% compared to the not optimized software (if I calculated it correctly :-p ).

 

To give you the real details: I'm using bitcoin mining software. I used to use poclbm, which is the most stable (and one of the older) GPU miners out there. Now I have switched to a recent Phoenix miner.

 

DoA HD5770 gave 190 Mhash/s

Old miner gives 165Mhash/s

New miner gives 210Mhash/s

 

Thank you for your help and advice, especially the one to not overclock it. At full load, I get 66°C peak, 63-64° average. Now it is stable, and I want to keep it that way.

 

-Y