SOLVED - Two 6990s different results. (1BTC Reward)

[Mezzan]

https://i.imgur.com/K46jy.jpg

https://i.imgur.com/UiEn1.jpg

It's kinda funny the difference between these two is about 100Mhash/s which is significant. I've been testing with different core and mem clocks for the first 6990 but still similar results.

INFO:
- Fan speed at 60% for both cards.
- FLAGS: -v -w128 -f1 (poclbm)
- Brand is PowerColor.
- First card uses 750W PSU, second uses 650W PSU.

Any ideas what went wrong? Or is it just the card?

Solution:
Set BIOS switch at "overclocked" position 1

[OmegaNemesis28]

Interesting 400MH/s on that second card.
My Visiontek 6990 only gets 340-370~ MH/s on both cores. The second core likes to be a little lower usually.

Are you running any flags?

[Mezzan]

Ah yes: -v -w128 -f1

[tman540]

Hey mezzan. I was having the same problem as well with my two 5830s. Personally, I've been using Sapphire TRIXX and I can crank out about 300 M/hash from both. I would suggest downloading it. Once you've installed it, before overclocking anything, click on the setting option. Uncheck Synchronize cards in Multi-GPU configs (I'm assuming you're mining with both cards via a dummy plug). Head over to the overclocking tab and change your settings to 945-975 Core Clock and 300-325 Memory Clock. Unless you want to go over 1000 Core clock, I suggest leaving the Voltage on stock.

After you've overclocked the first one, click on the down arrow. This will allow you to overclock your other video cards to the same settings. Make sure to press apply for each video card you over clock. You can save profiles so you don't have to always do it manually.

The fans will automatically adjust whenever you increase the Core Clock. If you'd like, you can set the fans to 75-90% by click on the fixed box under "Fan Control".

Click on info and double check to see if the clocks are showing he correct numbers.

HAPPY MINING!! Feel free to PM me if you have any questions!

[Xephan]

Is the first 6990 your primary display card and/or is it installed above the second physically?

[Mezzan]

6990 will not work if memory clock is 100mhz below core clock, it will freeze instead.

These two 6990's are on separate motherboards, basically two different computers.

[tman540]

6990 will not work if memory clock is 100mhz below core clock, it will freeze instead.

These two 6990's are on separate motherboards, basically two different computers.

Have you tried doing it with TRIXX?

[Xephan]

6990 will not work if memory clock is 100mhz below core clock, it will freeze instead.

These two 6990's are on separate motherboards, basically two different computers.

What happens if you swap the cards? Do the numbers follow the card or the motherboard?

[Mezzan]

Good idea but that's what I'm afraid of. I'm worried if i swap the cards the 800MHash/s card will not get that speed anymore even if i put it back but heck, I'll give it a try tomorrow since it's at my data center. I'll update on anything I find tomorrow.

I'll try with TRIXX as well.

[tman540]

Update us when you can. Like I said, try TRIXX if it allows you, I think it may solve your problem

[tman540]

http://www.geeks3d.com/20110616/gpu-shark-0-5-1-released/


trying using this on both cards and see if they are both GPU usages are at 99%.

[PLaci1982]

http://www.geeks3d.com/20110616/gpu-shark-0-5-1-released/


trying using this on both cards and see if they are both GPU usages are at 99%.

Look at the 1st picture, and you will see, that the slower Mh/s card are running at 99%

@Mezzan: Both PCs are running the same OS?

[Mezzan]

http://www.geeks3d.com/20110616/gpu-shark-0-5-1-released/


trying using this on both cards and see if they are both GPU usages are at 99%.

Look at the 1st picture, and you will see, that the slower Mh/s card are running at 99%

@Mezzan: Both PCs are running the same OS?

Yes both are using Windows 7 64bit, 2GB RAM each PC

[Desolator]

This seems a lot simpler than everyone is making it.  First of all, same driver, right?  Probably  The real answer is, just because you got 2 cards at the same time from the same vendor doesn't mean they shipped with the same BIOS version.  Yes, video cards have BIOS ROMS too, ppl.

1. Back up both BIOSes on each card to 2 separate files and name them with -slow and -fast at the end so you know which is which.

2. Update both of those cards to the latest version, not just the slowest one, and you should see more consistent results.

3. test the results

4. if they're both fast, yay.  If they're both slow, load both cards with the (at that point) older and faster BIOS version which should be the one you saved called something like "6990BIOS-backup-fast" and load that onto both cards.

If that doesn't help, the 2nd card is most likely receiving less voltage from the power supply.  Test it by swapping the supplemental power cables going to the cards with each other and see if the MH/s swap as well.

I think setting the clock speed means you're setting a target, not magically setting what reality is occurring in the card's GPU.  That'd be cool if they did that though cuz then you could set it at ANYTHING lol.  Either way, I know for a fact that a lot of overclocking utilities don't say what the clock speed is in realtime, they just list what the max/target speed is set at.  If the voltage has dips or is constantly a bit low, the card will downclock itself.  I think that shows up in the realtime meter shown in the nice free utility called GPU-Z as of at least version 0.5.4.  Watch the clocks on both and see if one keeps taking a dive or is operating slower than the OC setting you set it at.

If all that leaves you with no fix, turn the memory speed up slightly past 840 in tiny steps on the slower card.  I've heard reports of identical cards slowing down (but not THAT much!) if they don't operate at a specific random speed.  Like someone said they have two 5830's and one prefers 325MHz and one prefers 375MHz and both perform poorly outside of that exact number.

[Mezzan]

@Desolator: I ran GPU-Z and found out the first card has crossfire disabled.  image:

https://i.imgur.com/Yg2pq.jpg

https://i.imgur.com/HdkC2.jpg


I remembered installing catalyst control center on the first card but not second.  Can ATI CCC enable Crossfire? hmm.. best to try it.


EDIT: The first card actually has crossfire enabled when I selected the other GPU. BIOS version same for both.

[-ck]

Crossfire has been known to slow down cards on windows.

[Mezzan]

Crossfire has been known to slow down cards on windows.

The crossfire is enabled by default for the 6990 GPUs. Performance on my second card is nice but the first one is minimal since clock settings are same / similar.


fyi, first card uses 750W PSU, second uses 650W PSU.

[Xephan]

Crossfire has been known to slow down cards on windows.

The crossfire is enabled by default for the 6990 GPUs. Performance on my second card is nice but the first one is minimal since clock settings are same / similar.


fyi, first card uses 750W PSU, second uses 650W PSU.

The PSU used shouldn't be an issue. Have you restarted the first machine since discovering this?

[Mezzan]

Crossfire has been known to slow down cards on windows.

The crossfire is enabled by default for the 6990 GPUs. Performance on my second card is nice but the first one is minimal since clock settings are same / similar.


fyi, first card uses 750W PSU, second uses 650W PSU.

The PSU used shouldn't be an issue. Have you restarted the first machine since discovering this?

Yes I did a couple of times.

[Bloodred]

Are you using the same CPUs and more importantly the same motherboard model?
If it has more PCI-e slots try the slow card in other slots too.