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theboss
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August 11, 2011, 02:16:02 AM
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August 11, 2011, 02:22:09 AM
 #2

yup, that PSU should be able to work. the other hardware (mobo, CPU, hard drive, etc) barely take any power. just don't be overvolting the two cards too much

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August 11, 2011, 02:29:28 AM
 #3

I have 8 rigs running 4x6970's in them.  With the memory clocked down and the voltage dropped a little, each machine is pulling 1049W from the wall.  This means that the PSU is probably seeing around 950W on the input side.  These machines have AMD X3 445's in them with two of the cores disabled.  Only one stick of RAM is being used.  They are booting from a flash drive as well (no hard drive).

With a quality power supply, you could probably get by with a 1000W PSU if you keep the memory clocks down.  Underclocking the video RAM and undervolting the cards dropped 100 watts (at the plug) on each rig.  2x6990's will use a little less power than 4x6970's, but not by much.  Another thing to consider is that a PSU is usually most efficient around 75% load.  Coughing up the extra cash for more than a 1000W PSU might save some electricity in the long run.

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sveetsnelda
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August 11, 2011, 02:33:21 AM
 #4

I should add that these 6970s are slightly overclocked.  They are running at 940mhz instead of 880.  Memclock is at 685.  Voltage is at 1.1v

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August 11, 2011, 02:36:44 AM
 #5

With a quality power supply, you could probably get by with a 1000W PSU if you keep the memory clocks down.  Underclocking the video RAM and undervolting the cards dropped 100 watts (at the plug) on each rig.  2x6990's will use a little less power than 4x6970's, but not by much.  Another thing to consider is that a PSU is usually most efficient around 75% load.  Coughing up the extra cash for more than a 1000W PSU might save some electricity in the long run.
I have to agree all you need is 1000 watts. A 6990 only requires around 300 watts so that's 600 from the cards. If you get a good 1000 watt power supply you'll never have any worries.
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August 11, 2011, 02:39:06 AM
 #6

I think so. You have a single +12V rail, so you don't have to worry where the power's coming from. And your power supply can provide up to 984W on that rail. Each card is rated for 330W max, so that would be 660W for the two cards. The remaining 300W should easily cover a minimal system.

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August 11, 2011, 03:44:56 AM
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Here are two reviews tested the 12v on the Coolermaster and it was within the 5% maximum variation (0.6v on the 12v rail) at beyond 1000w load:
http://www.bcchardware.com/index.php?full=1&set_albumName=CM1000WGold&id=AveVoltage&option=com_gallery&Itemid=96&include=view_photo.php
http://xtremetechjunkies.com/2010/07/cooler-master-silent-pro-gold-1000w-power-supply-review/
However, both reviews used PSUs supplied by Coolermaster so who knows if they were cherry picked. Jonnyguru reviewed a similar Coolermaster PSU and the 12V rail was dangerously close to the limit when the 3.3v/5v were mainly left unused, which you would be doing. He is a much more reputable source for PSU reviews. On the plus side, all reviews showed the efficiency was still good.

The 6990 uses about 375w each so with overclocking two will pull some juice. As sveetsnelda advised, keep overclocking down and you should be good.
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August 11, 2011, 04:48:47 AM
 #8

i don't personally own a 6990, but there seems to be some conflicting numbers on the power consumption. so is it 300w, 330w, 375w, or 450w? i think i read the reviews on these and it has a stock TDP of 300w, and there's a flip of a switch that will bring performance up, where it has a TPD of 450w.

when i said that 2x 6990 should be able to work on this 1000w, i just assumed it was 450w TDP, which a 1000w quality PSU should be barely enough since video cards never pass that power limit, even at 100% load on stock clocks.

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August 11, 2011, 04:52:10 AM
 #9

I'm running 2 6990's on a coolermaster silent pro 1kw bronze, it has an i7 920 & 12gb ram & 2 x 1tb sata drives. Its been running perfectly for over a month now and my cpu is around 85% 24/7, ram around 10gb. I have the cards in the overclocked position @ 920/600. I do need to plug my kill-a-watt in at some point because I know I'm right on the limit if not probably over with the amount of cpu/ram usage.
I don't think you have anything to worry about, the PSU is rated for something like 1200w burst, 1000w continual and it comes with a nice lengthy warranty.

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August 11, 2011, 05:01:47 AM
 #10

i don't personally own a 6990, but there seems to be some conflicting numbers on the power consumption. so is it 300w, 330w, 375w, or 450w? i think i read the reviews on these and it has a stock TDP of 300w, and there's a flip of a switch that will bring performance up, where it has a TPD of 450w.

when i said that 2x 6990 should be able to work on this 1000w, i just assumed it was 450w TDP, which a 1000w quality PSU should be barely enough since video cards never pass that power limit, even at 100% load on stock clocks.
Correct.  Once you flip that switch and OC that card a little, I'm positive that two 6990's in a minimal system will draw somewhere around 1000 watts at the wall.

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August 11, 2011, 08:24:31 AM
 #11

I have 8 rigs running 4x6970's in them.  With the memory clocked down and the voltage dropped a little, each machine is pulling 1049W from the wall.  This means that the PSU is probably seeing around 950W on the input side.  These machines have AMD X3 445's in them with two of the cores disabled.  Only one stick of RAM is being used.  They are booting from a flash drive as well (no hard drive).

With a quality power supply, you could probably get by with a 1000W PSU if you keep the memory clocks down.  Underclocking the video RAM and undervolting the cards dropped 100 watts (at the plug) on each rig.  2x6990's will use a little less power than 4x6970's, but not by much.  Another thing to consider is that a PSU is usually most efficient around 75% load.  Coughing up the extra cash for more than a 1000W PSU might save some electricity in the long run.

The good side is that a 6990 will draw much less power than 2 normal 6970's, because the chips in 6990's are hand picked to work on the lowest possible voltages.
A 6990 at stock consumes only 375 watts while two 6970's consume about 500 watts.

The OC switch complicates things a bit as it will make the card consume 450 watts, so that's a total of 900W (bit more at the wall).
Counting in processor, ram, HDD, mobo power requirements, a quality 1kW supply could just about pull it off.

I do have one such setup, but with a Corsair 1200W PSU to be on the safe side.

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August 11, 2011, 04:26:50 PM
 #12

I have a 1350W PSU running 3x6990 just fine.  I don't have anything over- or under-clocked, and my hash rates are great (~2200 MH/s).  The system also includes an AMD Phenom 4C CPU at 2.66 GHz, 8 GB RAM, and other normal PC components to make it a usable system for gaming and such -- in case this whole bitcoin thing doesn't work out. Tongue
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August 11, 2011, 06:14:45 PM
 #13

I have a 1350W PSU running 3x6990 just fine.
what's the PSU efficiency and how many watts are you pulling from the wall?

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August 12, 2011, 01:42:17 AM
 #14

I'm going to say one thing, Dont use that 1tb as your main drive.
its going to get fragmented quick.

Use a smaller hard drive as your system drive and the 1tb as storage.
a 160 gig would be good for windows 7 to live on  even can live on 40 gig if you had to,.
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August 12, 2011, 01:54:44 AM
 #15

Im telling you from exeprience get a 1200 or 1500 watt good power supply.  I have had tests and builds with all the newest cards and PSU and 1000 watt corsair, Ultra and an ANTEC, combos of all those none of them wore running easiliy, all maxed out and caused issues.  Replaced with 1200s and 1500watt psus on 9 high dollar builds and no issues, well worth it if your overclocking cpu, gpu or both and running hard core or mining.

If you gotta go a 1000, get the ultra x4 1000 watt, if they blow u get a new one easy, used many of those.

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August 12, 2011, 02:04:20 AM
 #16

So im running 2X6990 on a 1200w psu

I saw a bitcoin miner review on the web that claims the 6990 can draw up to 600w's on full load?

http://www.hardocp.com/article/2011/07/13/bitcoin_mining_gpu_performance_comparison/4

Anyone have any comment on that?

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sveetsnelda
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August 12, 2011, 06:21:02 AM
 #17

I have 8 rigs running 4x6970's in them.  With the memory clocked down and the voltage dropped a little, each machine is pulling 1049W from the wall.  This means that the PSU is probably seeing around 950W on the input side.  These machines have AMD X3 445's in them with two of the cores disabled.  Only one stick of RAM is being used.  They are booting from a flash drive as well (no hard drive).

With a quality power supply, you could probably get by with a 1000W PSU if you keep the memory clocks down.  Underclocking the video RAM and undervolting the cards dropped 100 watts (at the plug) on each rig.  2x6990's will use a little less power than 4x6970's, but not by much.  Another thing to consider is that a PSU is usually most efficient around 75% load.  Coughing up the extra cash for more than a 1000W PSU might save some electricity in the long run.

The good side is that a 6990 will draw much less power than 2 normal 6970's, because the chips in 6990's are hand picked to work on the lowest possible voltages.
A 6990 at stock consumes only 375 watts while two 6970's consume about 500 watts.
It's true that the 6990's are binned to run at lower voltages, but a 6970 certainly doesn't consume 250W while mining unless it was *heavily* overclocked/overvolted.  I have 38 of them mining in various flavors.  They're pulling about 200 watts each while stock and about 220 watts each while slightly undervolted and slightly overclocked.  A 6990 will use something similar since it uses two of the same chips, but a very small amount of overhead is saved from them sharing power regulation, BIOS, video outputs, etc.

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August 12, 2011, 08:04:06 AM
 #18

I have 8 rigs running 4x6970's in them.  With the memory clocked down and the voltage dropped a little, each machine is pulling 1049W from the wall.  This means that the PSU is probably seeing around 950W on the input side.  These machines have AMD X3 445's in them with two of the cores disabled.  Only one stick of RAM is being used.  They are booting from a flash drive as well (no hard drive).

With a quality power supply, you could probably get by with a 1000W PSU if you keep the memory clocks down.  Underclocking the video RAM and undervolting the cards dropped 100 watts (at the plug) on each rig.  2x6990's will use a little less power than 4x6970's, but not by much.  Another thing to consider is that a PSU is usually most efficient around 75% load.  Coughing up the extra cash for more than a 1000W PSU might save some electricity in the long run.

The good side is that a 6990 will draw much less power than 2 normal 6970's, because the chips in 6990's are hand picked to work on the lowest possible voltages.
A 6990 at stock consumes only 375 watts while two 6970's consume about 500 watts.
It's true that the 6990's are binned to run at lower voltages, but a 6970 certainly doesn't consume 250W while mining unless it was *heavily* overclocked/overvolted.  I have 38 of them mining in various flavors.  They're pulling about 200 watts each while stock and about 220 watts each while slightly undervolted and slightly overclocked.  A 6990 will use something similar since it uses two of the same chips, but a very small amount of overhead is saved from them sharing power regulation, BIOS, video outputs, etc.

Off topic, but goodness 38 6970's must be loud.  I have 3 of them that whine like hell compared to Sapphire xtreme cards.
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August 12, 2011, 06:32:48 PM
 #19

Off topic, but goodness 38 6970's must be loud.  I have 3 of them that whine like hell compared to Sapphire xtreme cards.
They're actually not too bad...  The box fans on the window are louder.  I'm bringing cool air into the room from an evap cooler mounted in an adjacent room.  6 of the 6970's are reference cards and the other 32 have very good coolers (MSI 6970 Lightnings).  The reference cards are running at 65% fan speed and the non-reference are on auto.


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August 13, 2011, 12:45:01 AM
 #20

Im telling you from exeprience get a 1200 or 1500 watt good power supply.  I have had tests and builds with all the newest cards and PSU and 1000 watt corsair, Ultra and an ANTEC, combos of all those none of them wore running easiliy, all maxed out and caused issues.  Replaced with 1200s and 1500watt psus on 9 high dollar builds and no issues, well worth it if your overclocking cpu, gpu or both and running hard core or mining.

If you gotta go a 1000, get the ultra x4 1000 watt, if they blow u get a new one easy, used many of those.

What brand of 1200+ PSU have you had best results with?
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