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Author Topic: 4x Radeon HD 6990  (Read 9420 times)
SD57
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May 18, 2011, 10:26:16 PM
 #1

Has anyone tried?
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m4rkiz
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May 18, 2011, 10:31:05 PM
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will work only on linux as windows has 4 gpu cores limit
basically no different than http://blog.zorinaq.com/?e=42
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May 18, 2011, 10:45:39 PM
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will work only on linux as windows has 4 gpu cores limit
basically no different than http://blog.zorinaq.com/?e=42

Someone has probably tried it somewhere. You would definitely need about 2000 watts between at least 2 power supplies since overclocked they pull close to 400 watts a piece

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May 18, 2011, 10:55:12 PM
 #4

Also they will draw more power than specified via the PCIe slots, so you might kill your hardware this way.

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May 18, 2011, 11:01:06 PM
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Also they will draw more power than specified via the PCIe slots, so you might kill your hardware this way.

Why?  They don't draw power from the PCIe bus, they have external power inputs [8 and 6 or 8 and 8 .. not sure which; my 6970 has 8 and 6].  You are the first that I have heard indicate that the card somehow draws more power from the bus than spec allows for.

BTW, a decent motherboard will simply refuse to bring a card online if it is energy starved.  I have found this out for myself ASUS Rampage III GENE (small little thing, but a very nice board for what it is).

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May 18, 2011, 11:42:33 PM
 #6

Also they will draw more power than specified via the PCIe slots, so you might kill your hardware this way.

Why?  They don't draw power from the PCIe bus, they have external power inputs [8 and 6 or 8 and 8 .. not sure which; my 6970 has 8 and 6].  You are the first that I have heard indicate that the card somehow draws more power from the bus than spec allows for.

BTW, a decent motherboard will simply refuse to bring a card online if it is energy starved.  I have found this out for myself ASUS Rampage III GENE (small little thing, but a very nice board for what it is).

http://blog.zorinaq.com/?e=44

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Veldy
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May 19, 2011, 12:20:02 AM
 #7


Thanks for the link. 

I do wonder though, is the spec he is referring too 1.0, 2.0, 2.1, etc?  Are they even different in this respect [I haven't looked].  All I know is that my motherboard has absolutely no problem with the 5970 [slightly over-clocked core, but no tinkering with voltage].  My board will make a loud squealing sound at start up if there is too much power draw [and a red LED lit up somewhere that I couldn't see, but the power was always cut to my 6970 when I tried to put a 5850 in with it [I was pushing it with a solid 750W power supply anyway].  I suppose cheaper motherboards would just lock up outright.  Anyway, I suspect most recent boards work with AMD and NVidia and know what their upcoming products are going to be like and they design accordingly.  That article indicates a considerably higher draw on current though and that really doesn't make a lot of sense to me since I am not sure a board could be designed that much over spec without adding additional PSU connectors to the board [or the PSU itself also tends to be overspec for the very same reasons].  One thing you know is that AMD chipsets on most motherboards are going to support the new video cards that AMD is making, and thus, so will Intel, VIA, etc.

I am not an electrical engineer [or an electrician] and have only some mathematical knowledge of electronics via a couple of EE courses in college, so I may really have no clue what I am inferring here  Huh

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May 19, 2011, 12:46:10 AM
 #8

Yes, they do indeed draw power from the PCIe connector, even though they have additional power connectors.

He is referring to the ATX power spec.  12v power for PCIe slots is provided by only two pins in the ATX power connector, rated for 6 amps each.  He was pulling 7.4 amps over each pin, which was melting the shroud and likely caused permanent damage to his motherboard.  It probably would have started a fire eventually if he hadn't been actively watching it.

His solution was to bypass the ATX plug (and motherboard) entirely by spicing his PCIe extenders to accept power directly from the power supply.

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May 19, 2011, 12:53:01 AM
 #9

Also they will draw more power than specified via the PCIe slots, so you might kill your hardware this way.

Haha... no.  PCI bus limit is about 75W.  These have dedicated 8 pin PCI-E connectors.

--------------

The problem I see with 4 of these in a system is heat and the fact that 2000W = more than a 15A breaker will handle.  I'd say your best bet would be 2 rigs.

Plus if one goes down, everything isn't down.  Much better for reliability.

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Veldy
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May 19, 2011, 01:00:19 AM
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Yes, they do indeed draw power from the PCIe connector, even though they have additional power connectors.

He is referring to the ATX power spec.  12v power for PCIe slots is provided by only two pins in the ATX power connector, rated for 6 amps each.  He was pulling 7.4 amps over each pin, which was melting the shroud and likely caused permanent damage to his motherboard.  It probably would have started a fire eventually if he hadn't been actively watching it.

His solution was to bypass the ATX plug (and motherboard) entirely by spicing his PCIe extenders to accept power directly from the power supply.

I understand what he did.  What I don't understand is why most people are NOT seeing such issues.  I have shuffled my cards around quite a bit with my ASUS Rampage III Gene and there is no sign of warping, discoloration or any damage what-so-ever.  The slots are never even warm to the touch [or the board if I happen to touch it].  You have to reach down to unclip the card to get it out, so I have little doubt that the board integrity is sound.

Maybe older boards that are closer to spec or lower quality suffer from this issue as opposed to better and newer boards?  Like I said, my board gives out a shrill squeal if you attempt to boot with too much power draw [found that out after shuffling cards and forgetting to connect the power to the video card ... when I was experimenting with two cards in my case (answer is too hot and need a larger PSU)].  Even if there is enough power to boot, the board will disable the heavy card [in my case the 6970] when it detects that it can't adequately keep it supplied with sustainable power.  

Anyway, it is good to know.  I am sure the NVidia 580GTX and 590GTX have similar power consumption [if they know it is there, they will use it].

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Veldy
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May 19, 2011, 01:02:15 AM
 #11

Also they will draw more power than specified via the PCIe slots, so you might kill your hardware this way.

Haha... no.  PCI bus limit is about 75W.  These have dedicated 8 pin PCI-E connectors.

--------------

The problem I see with 4 of these in a system is heat and the fact that 2000W = more than a 15A breaker will handle.  I'd say your best bet would be 2 rigs.

Plus if one goes down, everything isn't down.  Much better for reliability.

Shouldn't four run somewhere around 1600W?  Still, you make a valid point.  It is like running a hair dryer 24/7 Sad

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grndzero
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May 19, 2011, 01:32:05 AM
 #12

Also they will draw more power than specified via the PCIe slots, so you might kill your hardware this way.

Haha... no.  PCI bus limit is about 75W.  These have dedicated 8 pin PCI-E connectors.

--------------

The problem I see with 4 of these in a system is heat and the fact that 2000W = more than a 15A breaker will handle.  I'd say your best bet would be 2 rigs.

Plus if one goes down, everything isn't down.  Much better for reliability.

Shouldn't four run somewhere around 1600W?  Still, you make a valid point.  It is like running a hair dryer 24/7 Sad

Yes, 4 cards would run at about 1600W but I would spec another 300 to run the rest of the system, thus arriving at about 2000 watts. Since the largest power supply I've seen is 1500 watts it would have to be broken up between 2 power supplies anyway. 2 x 1000 watt supplies each running 2 cards, 1 powers the motherboard and the other powers any other accessories ... hard drive, fans, etc.

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Veldy
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May 19, 2011, 01:54:35 AM
 #13

I would use a small and cheap SSD.  Save lots of power and very fast.  Most will new in memory anyway.  Static and small swap (with linux, perhaps no swap).

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foxmulder
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May 19, 2011, 05:53:38 AM
 #14

I currently running Quad 6990 on EVGA SR-2, i know it's overkill lol(my first mining rig mistakes), 2 PSU used, 1 Corsair AX 1200 for the barebone system + 2 6990, and silverstone strider gold 1000 for the next dual 6990, for the Hexa(Quad 6990) gpu setup on SR-2 you required additional 1x 6 pin connector plugged on the board as additional power to power up those pcie x16 lanes. Believe me it's not nice to run this monster on hot tropical places without additional cooling in your room, it output around ~7300 BTU heat.

The setup i used is open case with my own custom ghetto design  Grin, 2 deck of rack, 2 pcie extender for dual on the top, i will post the pics when i have the time.

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May 19, 2011, 07:03:11 AM
 #15

WOWOWOWOW!!!
Plz post your pics. Also it's very interesting to know if PCIe 8x or 4x wouldn't be a bottleneck when measuring MHash/s.
Please describe your setup as much detailed as you can. Very appreciated.

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May 19, 2011, 11:27:27 AM
 #16

And, please, post the software you are using.
SD57
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May 19, 2011, 11:32:35 AM
 #17

Performance slightly decreases in standard tests (~10%), and while mining you need even less communication with the card. Consider this video:
http://www.linustechtips.com/ltt-videos/radeon-hd-6990-bandwidth-comparison-test-16x-vs-8x-vs-4x-3dmark-11-linus-tech-tips
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May 19, 2011, 11:46:36 AM
 #18

I would use a small and cheap SSD.  Save lots of power and very fast.  Most will new in memory anyway.  Static and small swap (with linux, perhaps no swap).

Just a side note, you save like 10Watts going from HDD to SSD, it's not like some super huge mega power saving device. The two main power draws in a system are the GPU and the CPU, fans/harddrives/whatever are minor additions.

GPUS definitely do draw power from the PCI-E bus, don't kid yourself there. Many newer boards however have power options designed to draw additional power from the PSU to the board however to offset an increased load. It's still pretty harsh on a system to run that much through it.
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May 19, 2011, 11:57:13 AM
 #19

A PCI-E slot provides up to 75W, each 8-pin connector up to 150W, amounting to 375W for a card. This is one of the reasons why GPUs of 6990 have to be underclocked (830MHz instead of 880MHz in 6970 and 6950) for stable performance.
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May 19, 2011, 01:09:08 PM
 #20

What do you, guys, think about this kind of boards to increase number of graphic cards in one system?

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