Re: Dual 6990s

http://tpucdn.com/reviews/ASUS/Radeon_HD_6990/images/power_maximum.gif

from http://www.techpowerup.com/reviews/ASUS/Radeon_HD_6990/20.html Their reviews are the best on the web IMO. One of the reasons I'm an active member over there. These are max figures, meaning the most you could draw from the card (ie: 100% load Furmark etc etc). I do not know if the power consumption is for 830Mhz core, but I believe it is. In your review, they state that the power consumption goes up by 18W for 880 core, so total Power consumption for the 6990 st 880Mhz should be 356W. There is a memory voltage bump, I believe, between the 2 BIOSes however, so keeping the 830 core BIOS but OCing to 880Mhz and downclocking to 150 mem (default idle clock, which is much lower than that of a 5970!!!) should definitively drop the Power consumption. I'm inclined to say that 5970 at 5870 core speed and 300 mem would definitively need more power than a 6990 at 6970 core speed and 150 mem.

True, the 6990s power consumption should be lower, but it would be awesome to know how much lower. The chart gives some figures to work with, but it would be great to have some data from actual miners as well. I have a 5870 that differs 27W from the chart, for several reasons I'm sure. It would be great to see how much the 6990 can benefit from a memory underclock. It certainly seems like there is a lot of potential there.

I'm looking for reasons to justify the 6990 in a hashing machine. For me, it all comes down to value. New tech is fun and exciting, but if there is minimal benefit for massive price increases, there is no point for me to spend the extra money.

As far as resale value, every day I see used 5870s selling for more than I paid for a new one.

The machine they use to take the power from that is a Keithley Integra 2700, a 1600$ machine that measures from the pci-e slot.... W1zzard has been into reviewing since a long time as well.... I believe his results are very accurate

I wasn't suggesting that the results on the chart were inaccurate. He doesn't underclock his memory, which is my primary concern. Also, he probably isn't mining when he takes those readings! Hmm, his method wouldn't account for power supply efficiency either.

If it did, it wouldn't be accurate would it?

Let me clarify. I don't necessarily care how much power the cards consume, other than it's a nice guide. I care about how much power the cards consume when mining bitcoins (to the best of their ability)!

When comparing, you CANNOT take that number unless you are talking theoretically. Else it is VERY innacurate. at 356W, at 80% it takes 445W while at 85% it takes 418W. It depends on too many factors for it to mean anything

Do not forget that if you are solely using you computer for mining, you might as well take into consideration whole system power consumption.

I never said he should, just that he didn't. This is a good thing. It was merely a comment on some of the things that vary from his chart to actual mining usage!

Of course I take into consideration whole system power consumption. Why would I be concerned about how much power is saved from underclocking the memory if I wasn't looking to save power elsewhere? That said, most of my power consumption comes from the video cards. I am bothered about CPU usage with multiple cards in Windows though.

Again. Those numbers are a great guide, but I'm more concerned about actual mining usage. The main thing I'm looking for is how much power is saved on a 6990 by underclocking the memory, as it seems like it could be significant. His chart does me no good except give a reference point of max consumption. It would also be interesting to know if the card supports undervolting the memory.

Undervolting memory may only be supported through BIOS mods...

it would be interesting to know about power consumption at lower mem clocks. If you REALLY want to know, I can ask him, provided I give him enough $$. I would need something like 15~20$ I guess. If enough people want this and contribute, I can ask him ho much he wants, perhaps he would do the same for a 5870 and 5870 if he still has those too.