Dual 6990s

[MonzAa]

Guys, any thoughts dual 6990s?

Can I use any miner for the job? Do you expect hash rates to increase as drivers get better?

Would you opt for 4 X 5870 instead?

I'd like to hear from people already using them as well.

Many thanks

[1714928040]

1714928040

[1714928040]

1714928040

[1714928040]

1714928040

[1714928040]

1714928040

[nster]

Dual 6990s would do a fine job

[MonzAa]

Dual 6990s would do a fine job

Thanks for that. Would you as a miner get them over 4 5870s?

I'm about to get a rig... But can't decide. It's fair to say that both have their advantages.

[nster]

Dual 6990s would do a fine job

Thanks for that. Would you as a miner get them over 4 5870s?

I'm about to get a rig... But can't decide. It's fair to say that both have their advantages.

yes because when mining isn't very profitable, or if BTC crashes, you got a great GPU system, while 4x 5870 won't be worth anything. Besides, 2* 6990 is supposed to have a higher Hashrate than 4* 5870. Also, considering power draw, heat, space and motherboard needs, the 6990s are much better

[rezin777]

Besides, 2* 6990 is supposed to have a higher Hashrate than 4* 5870. Also, considering power draw, heat, space and motherboard needs, the 6990s are much better

Are you certain? I'm almost positive two 5870s will beat a single 6990 by a good margin at pure hashing power. Have you seen a 6990 hit over 700Mhash/s?

Also, isn't the 5970 faster than a 6990 while using less power?

I think the only drawback of the four 5870s is the spacing (and thus cooling issues) on a single motherboard. It will take more power to run 4 of them vs. 2 of the dual core cards, but you will be getting more hash/s from a single machine (which may or may not be cost effective).

[MonzAa]

My thoughts

5990 - I really think the the 5990 is underrated because not many people have been under the hood yet to fine tweak the miners, Hence the mundane stock rate right now of 0.6Ghps. But I read somewhere  that the card could potentially be 28% faster (not sure if some of that can be used for generating coins)

Also, the card will have a lot of resale value, miners will take most and what's left will be for the verrrry wealthy gamers and since this card is produced in limited quantities prices will go up.

2 * 5990 1.2Ghps 800ish Watts. 

CONS

The card consumes a beastly amount of energy - some quoting 445w under load.

5870 - two of these cards will give you 0.7Ghps, require less power, it can even be economic to just have in 4 in 2 crossfire motherboards (tri + quad fire way to expensive) Needing cheaper PSUs

4 * 5870 1.4Ghps 750ish Watts.

Man... My balance is 0.05 thank you faucet!

[rezin777]

My thoughts

5990 - I really think the the 5990 is underrated because not many people have been under the hood yet to fine tweak the miners, Hence the mundane stock rate right now of 0.6Ghps. But I read somewhere  that the card could potentially be 28% faster (not sure if some of that can be used for generating coins)

Also, the card will have a lot of resale value, miners will take most and what's left will be for the verrrry wealthy gamers and since this card is produced in limited quantities prices will go up.

2 * 5990 1.2Ghps 800ish Watts. 

CONS

The card consumes a beastly amount of energy - some quoting 445w under load.

5870 - two of these cards will give you 0.7Ghps, require less power, it can even be economic to just have in 4 in 2 crossfire motherboards (tri + quad fire way to expensive) Needing cheaper PSUs

4 * 5870 1.4Ghps 750ish Watts.

Man... My balance is 0.05 thank you faucet!

I think you mean 6990 when you say 5990? Have you looked at the 5970 compared to the 6990?

With some searching, there are used, last generation, quad pci-e x16 boards to be had for much less than you'd expect.

[nster]

The 6990's Power consumption after mem clock reduction, is lower than that of a 5970 after reduction

2* 5870 takes 424W, 1* 5970 = 304W, 1* 6990 = 338W. This is without downclocking mem. The 6990, with it's massive 4GB and higher mem clock, has more benefits from the downclock, hence, less power usage than that of a 5970.

A 6990 outperforms a 5970, so I'm guessing it outperforms 2* 5870s too. If not, then it isn't far. Best $/Mh is still the 5970. I'd still get 6990s as I find investing in old tech for something that isn't for sure is not smart, at least the 6990 has resell value and better usability in other applications

[rezin777]

The 6990's Power consumption after mem clock reduction, is lower than that of a 5970 after reduction

2* 5870 takes 424W, 1* 5970 = 304W, 1* 6990 = 338W. This is without downclocking mem. The 6990, with it's massive 4GB and higher mem clock, has more benefits from the downclock, hence, less power usage than that of a 5970.

A 6990 outperforms a 5970, so I'm guessing it outperforms 2* 5870s too. If not, then it isn't far. Best $/Mh is still the 5970. I'd still get 6990s as I find investing in old tech for something that isn't for sure is not smart, at least the 6990 has resell value and better usability in other applications

Interesting, I hadn't heard this about the 6990 elsewhere.

It would be fantastic if there was a simple way to decrease the voltage to the memory on any of these cards. I have yet to find a solution on the web.

[goatpig]

The 6990's Power consumption after mem clock reduction, is lower than that of a 5970 after reduction

2* 5870 takes 424W, 1* 5970 = 304W, 1* 6990 = 338W. This is without downclocking mem. The 6990, with it's massive 4GB and higher mem clock, has more benefits from the downclock, hence, less power usage than that of a 5970.

A 6990 outperforms a 5970, so I'm guessing it outperforms 2* 5870s too. If not, then it isn't far. Best $/Mh is still the 5970. I'd still get 6990s as I find investing in old tech for something that isn't for sure is not smart, at least the 6990 has resell value and better usability in other applications

care linking your source? I've got different numbers:

http://benchmarkreviews.com/index.php?option=com_content&task=view&id=706&Itemid=72&limit=1&limitstart=16

5970 on load = 299W
6990 on load = 350W

This indeed doesn't take in account the power saved through ram underclocking, and i think it is quite possible to get the 6990 to run in the lower 3xx, but I doubt it'll fetch below 300. I don't know how faster the 6990 is compared to the 5970, but I wonder if it justifies the $700 price tag considering you can get 5970s on ebay for less than $450 shipped. At any rate, you can get three 5970 for the price of two 6990. Better $/MHash for sure.

As for four 5870, they'll definitely draw more power than two 6990. Although single gpu cards o/c much better, so I wonder if a 6990 combo could beat four 5870.

[mrb]

Are you certain? I'm almost positive two 5870s will beat a single 6990 by a good margin at pure hashing power. Have you seen a 6990 hit over 700Mhash/s?

One 6990 beats two 5870 because the VLIW4 architecture is easier to fully exploit than VLIW5 arch. I benchmarked my miner, hdminer:

• One 6990 (switch at position 2, ie. 830MHz): 683 Mhash/s
• One 6990 (switch at position 1, ie. 880MHz): 723 Mhash/s was an error, I measured: 746 Mhash/s
• Two 5870: 664 Mhash/s (332 Mhash/s each)

However, price-wise it makes more sense to buy two 5870.

[goatpig]

Are you certain? I'm almost positive two 5870s will beat a single 6990 by a good margin at pure hashing power. Have you seen a 6990 hit over 700Mhash/s?

One 6990 beats two 5870 because the VLIW4 architecture is easier to fully exploit than VLIW5 arch. I benchmarked my miner, hdminer:

• One 6990 (switch at position 2, ie. 830MHz): 682 Mhash/s
• One 6990 (switch at position 1, ie. 880MHz): 723 Mhash/s
• Two 5870: 664 Mhash/s (332 Mhash/s each)

However, price-wise it makes more sense to buy two 5870.

5870's can squeeze 360mhash each with an average o/c on stock voltage.

[mrb]

5870's can squeeze 360mhash each with an average o/c on stock voltage.

Apples vs. oranges. The 6990 too can easily be overclocked beyond the "factory" 880MHz.

[goatpig]

5870's can squeeze 360mhash each with an average o/c on stock voltage.

Apples vs. oranges. The 6990 too can be overclocked.

Although single gpu cards o/c much better, so I wonder if a 6990 combo could beat four 5870.

[mrb]

Although single gpu cards o/c much better, so I wonder if a 6990 combo could beat four 5870.

Of course it would. Bitcoin mining scales linearly with the # of GPUs, so a pair of 6990 at 880MHz would achieve 1446 Mhash/s, compared to 1328 Mhash/s for four 5870.

It is kind of pointless to argue which one would be faster when overclocked beyond the factory setting, because the overclocking room varies so much from card to card, and with the type of cooling (air, water, etc).

[rezin777]

Are you certain? I'm almost positive two 5870s will beat a single 6990 by a good margin at pure hashing power. Have you seen a 6990 hit over 700Mhash/s?

One 6990 beats two 5870 because the VLIW4 architecture is easier to fully exploit than VLIW5 arch. I benchmarked my miner, hdminer:

• One 6990 (switch at position 2, ie. 830MHz): 682 Mhash/s
• One 6990 (switch at position 1, ie. 880MHz): 723 Mhash/s
• Two 5870: 664 Mhash/s (332 Mhash/s each)

However, price-wise it makes more sense to buy two 5870.

Do you happen to know the power consumption of that card at 723 Mhash/s?

[goatpig]

Although single gpu cards o/c much better, so I wonder if a 6990 combo could beat four 5870.

Of course it would. Bitcoin mining scales linearly, so a pair of 6990 at 880MHz would achieve 1446 Mhash/s, compared to 1328 Mhash/s for four 5870.

It is kind of pointless to argue which one would be faster when overclocked beyond the factory setting, because the overclocking room varies so much from card to card, and with the type of cooling (air, water, etc).

Are you certain? I'm almost positive two 5870s will beat a single 6990 by a good margin at pure hashing power. Have you seen a 6990 hit over 700Mhash/s?

a question on that subject was brought up, so i answered it.

The point was that even though the 5870 is the worst Mhash/W ratio of the 3 choices mentionned, it's the best Mhash/$, partly cause it can overclock so well when compared to dual gpu cards. This is relevant to the choice of cards imo.

Now, let's admit that four 5870's hash like two 6990, it would cost $700~800 to get the 5870s off of ebay, and $1400 for the cheapest 6990's out there. At worst this is a $600 difference. Assuming the 5870's run at 200W/h and the 6990 at 250W/h (im taking large figures here on purpose) you'd be at a 300W deficit per hour with the 5870's. At an expensive $0.20/kW(exagerating figures again), you'd be paying an extra $1.44 electricity per day compared to the 6990's. At this rate, the 6990's will close the gap in 416 days, or a little short of a year and 2 months. I'd take the 5870's, not to mention that you can build up to it slowly with the profit generated by cumulative card purchase.

[mrb]

I agree with you goatpig. I said from the beginning that price-wise the 5870 is more economical.

[goatpig]

I agree with you goatpig. I said from the beginning that price-wise the 5870 is more economical.

Indeed. Anyways, do you have extra data to share on the 6990, like power consumption, how low can the ram be underclocked and what not?

[nster]

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.