Bitcoin Forum

Hi all.

I have been playing around with overclocking my cards, 2x5850 1x5870, but I'm not sure I'm doing it right.

My 5850's are clocked at 885/300 and spit out around 366mh/s, I think that's not too bad. The 5870 on the other hand, I have a feeling Im not pushing enough. It's currently clocked at 910/300 and spitting out ~412mh/s. When reading up on other people's results, I noticed that different memory speeds are used, generally between 300-350, how does the core clock correlate to the memory clocks?

How much should I push a card? It may seem as a stupid question, but other than BSOD's, freezing up, rebooting the pc, is there things that can indicate unstable OC? Noticed at higher clocks my miner restarts more often, but to be honest I cannot rule out that it's simply something with the internet-connection between me and btcguild (Im in Europe). Higher overclocks also gives me higher stale counts, can raising the memory speed decrease those? The system itself does not hang or anything, so that is why I'm not sure if the cards are pushed enough. Should I just overclock till the system restarts, shows visible graphic errors, etc, and then set the core clock down like 5-10mhz?

I am using Windows 7 32bit, AOCLBF 1.75, Phoenix 1.5 with the 07-17-11 kernel, AMD 11.7 with included SDK.
Motherboard Asus P5K, C2D e6850 (or e6750, can't recall atm) 2x1gb RAM, Wireless network card (could that mess with my stale share count/miner restarts?)
Two Sapphire Xtreme 5850's and one XFX 5870 HD-587X-ZNFV.

Any help would be greatly appreciated.

I want to start out by saying I won't have my first 5850 until Wednesday so I can't really help with specific clock numbers. I know the 5830's best memory clock is 350 any more then that does nothing any less the megahash starts to drop. You just need to look up what people are saying for memory for the 5850 and test going up and down seeing where the sweet spot for your card is. The reason you drop the memory is because you get nothing extra from from the memory being so high. By lowering the memory you'll make the card run cooler, it will consume less electricity and as a side effect of the lowered heat allows you to push the core clock higher.

Each 5850 and brand of 5850 is different my suggestion is find what seems to be the average overclock speed(that is higher then what you have now) and try it. If the drivers crash or the heat is too high lower the core clock a little until its at a safe temp.

Did I miss anything you wanted answered?

Thanks for your reply.

I know why the memory speeds are lowered, and I think 300 is good for the 5850's, I was more wondering about the 5870, have been looking at the Mining Charts, looking through forums, and it's hard to get an idea of the current popular/working memory speeds. The other thing I wanted to ask about was how much I should push the overclock, until the drivers crash/system hangs/reboots? What about the random miner restarts and increased stales? Could it be a sign of approaching the OC limit? Or is it more likely that it's because of my wireless network card.

The temps shouldn't be a problem, I made a custom case (ugly as ****, but works) and have a huge room fan just next to it, the hottest card gets around 67 degrees celsius if it's really hot outside.

You should push the overclock to where you feel comfortable most 58xx cards are ok between 975-1025 mhz easily but it does vary card to card. I set myself a target of 1ghz on each card which is normally easy enough to each with little more than a mild voltage increase. be careful of your temperatures and keep in mind you may not be able to reach the highest listed speeds on the compairson chart with every card.

Be very careful when messing with the voltages that can seriously mess up your cards if you blindly change the amount. When it goes to changing the core clock you'll probably be fine trying the high end (around 1 ghz) and if it crashes lower the clock. A couple driver crashes aren't going to do serious damage to the card.

yeah forgot to mention that i wouldnt go past 1.225 volts unless i was in a really bad mood

Forgot to mention, I am not too willing to overvolt, as far as I can understand, the increase in power usage is too big compared to the mh/s gained.

Perhaps I'm looking for too much, since not all cards are made equal, and there is a reason for why the 5870 is set to 850mhz stock and not 900, but I feel that I'm cheating myself with a 50-60mhz overclock, and from reading the forums, I get the idea, I should be able to get it a bit higher, even on stock volt.

Any experience from people with 5870's with regards to the OC would be great, especially memory speeds.

And again with regards to stability, I get the idea that it's not small signs you look for (i.e. miners restarting), but drivers crashing, BSOD, reboot, etc.

I have a 5870 it's this one specifically http://www.newegg.com/Product/Product.aspx?Item=N82E16814102872
it runs fine at 1000mhz even with 500 mhz memory i've upped the voltage to 1.21 but i might be able to cut it back a little if i was to tinker with it. below 400mhz the card stops mining within the hour and it's far more stable at 500mhz the system had been up for 7 days till i tripped a breaker last night(3 mining rigs + window ac > 15 amp)

i've gotten my 5850's to run about 390 mh/s stable, using 1187 voltage, and over clocking them to 970 mhz hope that helps!

Thank you for all the replies. I am still playing around with the settings, but have been able to run the 5850's @ 900/300 and the 5870 @ 945/325. 5850's are spitting out 375Mh/s and the 5870 436Mh/s. Everything at stock volts.