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2 x 7990's or 4 x 7990's

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April 9, 2013 5:13:52 PM

Hey guys,

I'm into bitcoin mining and so am looking to set up a new and improved rig.

I've got some 7990's in mind, Ideally I'd love some way of running 4 through 1 mobo but everything I've seen seems to say that's not a realistic option.

2 x 7990's sounds like a different story though, and advice on a board that would be suited to/capable of taking 2 would be really helpful.

Am I right in thinking a 1200w 80plus Platinum Corsair pwr supply would be suitable for 2 x 7990's?

Any help is appreciated!

More about : 7990 7990

a b U Graphics card
April 9, 2013 5:20:31 PM

Hi :) 

I run a 7990 ...this one >>> http://www.powercolor.com/us/products_features.asp?id=4...

The problem you will face is size.... they are truly massive... length PLUS WIDTH....

You will NOT get 4 into any motherboard I know of but you should get 2 in as long as its a server case, with a full size motherboard.... and LOTS of ventilation.... and earplugs lol...they are LOUD at full chat...

Psu..I use an 850 for one....so a GOOD MAKE 1200 would do for a pair....

Just out of interest, can you make enough money from Bitcoining to pay for 2 x 7990 ?

All the best Brett :) 
April 9, 2013 5:23:16 PM

I wouldn't think that it is possible to have 4 7990's on one board because one 7990 is effectively 7970s in crossfire so therefore you probably can only get 2 7990's to work together (this is just off the top of my head though, not concrete info). That PSU would be fine I'm pretty sure, honestly if you're gonna do bitcoin mining isn't the gtx 690 better purely because of the power consumption? Your power bill difference might be quite big (idk about pricing in your area). Any motherboard with two 16x slots should work perfectly fine for 2 7990s (you could use a 8x slot for one of them but I think that might limit a card with that much power)
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a c 175 U Graphics card
April 9, 2013 5:23:51 PM

First of all, before you do this, be aware that ASIC miners should appear within the next month or two. They will do to GPU mining what GPU mining did to CPU mining, i.e. render it obsolete.
I suspect you may still have time to recover your investment on a single HD7970, maybe even two of them, but that's it. Of course, I could be wrong, but you're talking about a significant chunk of change here.
a c 175 U Graphics card
April 9, 2013 5:26:04 PM

DelightfulDucklings said:
...honestly if you're gonna do bitcoin mining isn't the gtx 690 better...

NO! NVidia cards don't mine worth pooh. Check some online resources. This is perhaps the one AMD vs. nVidia issue that is utterly beyond any debate.

April 9, 2013 5:28:07 PM

I take back my gtx 690 recommendation for bitcoin mining. They suck at mining seemingly
April 9, 2013 5:29:01 PM

Onus said:
DelightfulDucklings said:
...honestly if you're gonna do bitcoin mining isn't the gtx 690 better...

NO! NVidia cards don't mine worth pooh. Check some online resources. This is perhaps the one AMD vs. nVidia issue that is utterly beyond any debate.



yeah sorry, just did a bit of reading about bitcoin mining and discovered exactly what you just said

a b U Graphics card
April 9, 2013 5:31:25 PM

Onus said:
First of all, before you do this, be aware that ASIC miners should appear within the next month or two. They will do to GPU mining what GPU mining did to CPU mining, i.e. render it obsolete.
I suspect you may still have time to recover your investment on a single HD7970, maybe even two of them, but that's it. Of course, I could be wrong, but you're talking about a significant chunk of change here.


Hi :) 

Can you make that sort of money then? 7990 money ?

I have several machines with them in, but do SETI instead...


All the best Brett :) 
a c 185 U Graphics card
April 9, 2013 5:39:33 PM

LMAO!Why on earth would you need two of these things?I can recommend you a good motherboard if you tell me your cpu ?
a b U Graphics card
April 9, 2013 5:40:56 PM

bigcyco1 said:
LMAO!Why on earth would you need two of these things?


Hi :) 

To make money I assume....I do know that ATI cards are REALLY good for Bit mining...

All the best Brett :) 
April 9, 2013 5:54:28 PM

Cheers for the good quick replies!

Brett: To deal with the noise I was considering watercooling with these-
http://www.techpowerup.com/180208/EKWB-Officially-Relea.....
That shouldn't effect the ability to have 2 on the same board (space/size-wize)?

DD: From what I've heard these are pretty much as good as it gets for GPU mining.. Alot of ppl have mentioned that 4 x 7970's could be a good alternative to this. Can Anyone explain what the difference would be with regards to power consumption and heat issues. If they're watercooled would that change things?

Onus: Yeah I think you're spot on Onus, I actually have a few ASICS "on their way" now too.. But there's other coins to be mined as well. To be completely honest with you, this is as much of a hobby idea as a money marker.. I'm really not going to know what it's worth until I set it up and see. My power (in Australia) is relatively high compared to the US and other place unfortunately and luckily we're going into winter because 50% of the year is HOT here.

Bigcyco: I don't have the CPU set in stone yet. I feel like I'm asking you to spoon feed me a bit, but could you give me your take on a good combination- 2 x 7990's +...... MOBO+ ......CPU.

Thanks guys!
a b U Graphics card
April 9, 2013 6:07:23 PM

nmx said:
Cheers for the good quick replies!

Brett: To deal with the noise I was considering watercooling with these-
http://www.techpowerup.com/180208/EKWB-Officially-Relea.....
That shouldn't effect the ability to have 2 on the same board (space/size-wize)?

DD: From what I've heard these are pretty much as good as it gets for GPU mining.. Alot of ppl have mentioned that 4 x 7970's could be a good alternative to this. Can Anyone explain what the difference would be with regards to power consumption and heat issues. If they're watercooled would that change things?

Onus: Yeah I think you're spot on Onus, I actually have a few ASICS "on their way" now too.. But there's other coins to be mined as well. To be completely honest with you, this is as much of a hobby idea as a money marker.. I'm really not going to know what it's worth until I set it up and see. My power (in Australia) is relatively high compared to the US and other place unfortunately and luckily we're going into winter because 50% of the year is HOT here.

Bigcyco: I don't have the CPU set in stone yet. I feel like I'm asking you to spoon feed me a bit, but could you give me your take on a good combination- 2 x 7990's +...... MOBO+ ......CPU.

Thanks guys!


Hi :) 

Regarding the water cooling plates.... it would make the card THINNER but... you would still need the plastic prop (the black rod thing that comes with the cards.... its to support the cards from bottom of case because they are so heavy...but as long as they would sort of jam on the wc plate it would be fine I think...the second prop would have to jam on the first card...

All the best Brett :) 
a b U Graphics card
April 9, 2013 6:09:30 PM

Hi :) 

Regarding cpus.... I run 1100Ts in mine .... Phenom 6 cores...perfect for gaming...does Bit mining also use the Cpus ?

All the best Brett :) 
a c 175 U Graphics card
April 9, 2013 6:33:38 PM

BigMack70 said:
IMO you're taking a fairly large risk thinking of grabbing multiple 7990s for BTC mining right now... it's extremely profitable at the moment (I'm making ~0.1 BTC/day = ~$23/day at current exchange rates but ASICs are coming sooner or later.

Unless BFL is a total scam, making a serious investment in GPUs for mining today is extremely risky. I would only recommend investing in what you can also use for other purposes e.g. gaming, if your investment vehicle of choice for BTC is graphics cards.

This. BFL=Butterfly Labs, one of two companies getting ready to ship ASIC miners.
1BTC was over $200 this morning. I'm going to run my HD7870 for a week or two (as soon as the bitcoin client synchronizes), and if it makes even a little money (should be around $50-$60), I'll get at least 1 HD7970 (which I can also use for games) and do it more aggressively, depending on whether the ASICs are out.
a c 243 U Graphics card
April 9, 2013 6:53:31 PM

I was just reading about how good ASIC miners actually are. Apparently some guy made back the $1200 he spent on the machine in 9 days! Very tempting to get in on that early. Those results are not typical of course but anything even approaching that would be amazing.
a b U Graphics card
April 9, 2013 6:58:12 PM

Hi :) 

Lol..I have a LOT of very powerful machines running SETI and i am around number 200 in the World.... and almost all on big ATI cards...

By the sound of it I might make some money but not sure its worth the bother ? :) 

All the best Brett :) 
a b U Graphics card
April 9, 2013 7:47:31 PM

*Cough* Electricity bills *cough*
April 9, 2013 8:40:43 PM

Can someone explain what is Bitcoin Mining?
a c 243 U Graphics card
April 9, 2013 8:52:52 PM

aonor said:
Hey guys! I think I found a motherboard that would support 4 x 7990!

http://www.newegg.com/Product/Product.aspx?Item=N82E168...


It's not the board it's that Crossfire only supports a max of 4 GPUs. Since an HD 7990 is already a dual GPU you are limited to 2 x 7990s. There maybe a hack around that though that I don't know about but officially 2 x HD 7990s are it.
a c 169 U Graphics card
April 10, 2013 2:46:16 AM

cookybiscuit said:
*Cough* Electricity bills *cough*


exactly. the electricity bill at the end of this will outweigh any money made. Unless you have solar power......
a c 175 U Graphics card
April 10, 2013 6:38:45 AM

Power bills for AMD cards are well under what they can make mining, even if 1BTC drops down to $15. It's nVidia cards that can't outmine their power use.
FPGA miners aren't notably faster than GPUs, but they use a lot less power. ASICs use a fraction of the power GPUs need, for 100 times the mining power.
Anyway, I've got my mere 400 MHash/s miner running.

Multiple graphics cards used for mining are not running in Crossfire; they're independent. Theoretically, you could mix graphics cards; e.g. I could add a HD7970 to the same PC that has the HD7870 in it (if my PSU supported it, which it does not).
April 10, 2013 7:17:29 AM

Well, there currently isn't an official Radeon HD 7990, so I guess we would have to see. Maybe try GTX690 or Titan?
a c 175 U Graphics card
April 10, 2013 8:07:36 AM

Hilarity; RussK1 tested his 680s and was getting 120 Mhash/s. A HD5670 beats that. No, nVidia can't mine worth pooh.
July 20, 2013 11:56:57 AM

nmx said:
Hey guys,

I'm into bitcoin mining and so am looking to set up a new and improved rig.

I've got some 7990's in mind, Ideally I'd love some way of running 4 through 1 mobo but everything I've seen seems to say that's not a realistic option.

2 x 7990's sounds like a different story though, and advice on a board that would be suited to/capable of taking 2 would be really helpful.

Am I right in thinking a 1200w 80plus Platinum Corsair pwr supply would be suitable for 2 x 7990's?

Any help is appreciated!


Power wise you should be fine with a 1200w but like some people have mentioned you will run into the same 2 issues I did, Sound and Temperature. I was able to fix both problems as well as the space issue by installing the EK waterblock which made the card smaller, reduced noise since I'm not having to run 3 super loud fans on max and my temps never go over 57. My current roadblock is that I cant overclock the card's Core beyond 1100MHz. I can get an easy 1.173Ghash/s with one card using GUIMiner and not heating the card beyond the 57c thanks to the waterblock.
!