Crossfire mining

[gonzas144]

Hi.

How I must set my GPUs?. One per worker? or both in one worker?.

In deepbit I had one worker for both video cards, but in BTCMine that method didn't work, I had to set a 2nd worker for my 2nd GPU. How about BTCGuild ?. I have to set 2 workers, one per GPU?.

[1713524460]

1713524460

[kodess]

workers are there for a reason, 1 GPU = 1 worker
it keeps it organized and optimized

[grue]

workers are there for a reason, 1 GPU = 1 worker
it keeps it organized and optimized

organized? yes. optimized? not really.

[grue]

how to you crossfire 3 cards ?

get 3 cards with 2 crossfire connectors each. :p

[GreenSky]

I recommend not crossfiring your cards, and instead using a VGA dummy plug for each.

[grue]

I recommend not crossfiring your cards, and instead using a VGA dummy plug for each.

can you explain more

1. search for "VGA dummy"
2. you're done!

[gonzas144]

I recommend not crossfiring your cards, and instead using a VGA dummy plug for each.

Hi. I've tried to disable the crossfire but when is it disabled one of the GPU's doesn't work. I know that in Linux is not mandatory to use the crossfire bridge. Im not getting bad performance with crossfire enabled though.

282 MH/s in both HD 6870.

[ensign_lee]

I have one of my rigs crossfired and I am noticing 0 difference in mining between doing that and running each monitor independently, as one datapoint.

[HudsonStan]

I have one of my rigs crossfired and I am noticing 0 difference in mining between doing that and running each monitor independently, as one datapoint.

Me too. What is real difference VGAdummy vs. CF? 0! I have 2x5870 a 2x6950. No difference. Bonus of CF is ability to use rig as mighty CF gaming rig.

[anodyne]

I feel I need to bring up a question related to this:

Why are "disconnected" secondary cards disabled in Windows (and as I understand it only in versions after XP)? Power saving feature? Something related to HDCP?

[mattpker]

What is the downside to running crossfire and mining with one worker? Will this have less Mhash/s then doing two cards/no crossfire and one worker per card? Does anyone have any data for this or links?

[icolsuineg]

Erm.. one miner doesn't load both GPUs, you will use send one for the second GPU. CF is used only to avoid driver disabling the second GPU, which can be avoided by using VGA Dummy Plug instead of connecting the cards with CF bridge and using CF. On a side note, CFed cards do eat more CPU power, and that is more watts wasted on the CPU. Oh, also keep in mind that remote connections (RDP, Teamviewer, etc.) usually disable/don't allow CF, which makes dummy plugs somehow better permanent solution - and it is a cheap one as you have the DVI-VGA adapter with every card and the resistors you need cost like few cents.

Still, my all VGA Dummy machine still eats a lot of CPU power, so...

[mattpker]

I thought that crossfire makes 2 cards one, did not know that the OS could still see them separately. So what you are saying is that I can run crossfire but will still be able to run one worker per GPU? Power consumption is not a problem for me as I have included utilities.

[mattpker]

This "sharing the workload" cause more/less/equal Mhash/s compared to using the VGA Dummy?

[ensign_lee]

This "sharing the workload" cause more/less/equal Mhash/s compared to using the VGA Dummy?

Should be EQUAL, according to my experience.

[mattpker]

Getting my two 6950's in a few days, will update this with my findings.

[Lars]

282 MH/s in both HD 6870.

What clock speeds, client and settings do you use for this? I get slightly less on my 6870s.

[warsmith]

I just tried mining with crossfire, with a pair of 6950s. They don't do an identical job. In fact, it is quite noticeably lower. I don't know why, but when I run them separately, they both go to 99% usage, and produce around 400MH/s each. When crossfired, they hover around 89-92% of usage both, and produce up to 20% less MH/s in total.

Any idea how to make them go up to 99%?

[gonzas144]

282 MH/s in both HD 6870.

What clock speeds, client and settings do you use for this? I get slightly less on my 6870s.

WORKSIZE=128 VECTORS AGGRESSION=9 FASTLOOP BFI_INT

6870 @ 970mhz, memory at 500 mhz.

[mattpker]

So I got my 6950's. Crossfire worked fine with assigning 1 worker per card. You were right though and this caused high CPU load. I turned off the Crossfire and luckily I did not need a VGA Dummy as I run dual head (two monitors with one pluged into each GPU). This produced the same Mhash/s but less CPU usage and more stability.