You know, I used to think that, but I have spent a long time looking at 4 screens rotating between 16 machine each on kvms.
I also have quite a few machines/cards mining (see sig).
While you may have momentary high burst of hash power, you really are only getting 70% at the min and maybe 90% at the max.
I don't see this behavior on my rigs... I'll get into that below.
Using onboard gpus will not affect wattage (or every mobo I have with one lies on my Kill-a-watts).
Er... Sort of. That assumes you're using a board with an onboard GPU in the first place. I'm not. I assure you that you'd see slightly less power used if the board *didn't* have that onboard GPU. If you already have it, then yes -- using what's already there wont significantly affect wattage. If your onboard GPU doesn't use any power or generate any heat, it's supernatural and magic.
Now your still going to say this will not be a big loss, but over a month, its huge. Look at your shares for your main gpu and look at the rest, 70-80% diff. If you are a true miner, you should not have more than 4 cards on your board anyway for a bunch of reasons. But having a display only card will not kill you, especially if you are not using it for heavy acceleration.
15 of my rigs have 4 GPUs and they don't exhibit this behavior. Maybe it's something specific to your setup? All of these rigs except for 1 (my main PC) are headless. Most of my rigs currently have about a 2 week uptime and I don't see the disparity between cards on any of them. In fact, on some rigs, I have slightly *more* accepted shares on GPU0. Even then, the highest share difference I can find between GPUs on *any* of my rigs is 0.269 percent.
I forgot to lock the topic, and will do so in the morning. Until then, ask some questions, then I will answer and lock to keep this as a reference topic.
Yeah, sorry about that. I realize that you wanted to lock the topic and have PMs, but I wanted to post this publicly to reduce what is [possibly] misinformation. It wouldn't be a public forum without public discussion.
Here's what I'm using for my 4 GPU rigs:
ASRock 870 Extreme3
Athlon II X3 450 with 2 cores disabled (overkill, but the resale will be higher if I sell assembled machines)
4x 5870's, 4x6970's, 4x6870s, and a couple machines with 2x 5970s.
OCZ ZX 1250W PSUs, OCZ ZX 1000W PSUs, OCZ ZX 850W PSUs, and a few various Seasonic PSUs (all 80PLUS Gold)
No hard drives (just 8gb and 16gb flash drives). Hard drives add a little extra power/heat to the mix (though you save $8-10 per machine if you happen to have a bunch laying around).
All dedicated rigs are running 32 bit Ubuntu Natty.
28 days into runtime, here is what we had. Both the Foxcon with the onboard and the Msi with the Hd5450 had around 20% more shares and while visible but unexplainable, less rejected shares by 4.5% (calculations became finite for rejected shares as this made no sense)
Again, I just don't see this behavior on any of my miners... unless I'm actually using the machine to browse, etc (on my Windows box). I saw this to some degree back when I was using Linuxcoin and Phoenix. Maybe that's the issue? If you would like some statistics from my miners, I'd be happy to send them to you.