Powering an 9800GX2 SLI Rig

Computer_Freak

Computer_Freak

Active Member
ok well my dad is going to the states and Im gonna get a GX2 (its the same price as a GTS here :p)

Now, in my later stage i will SLI 2 together. How much power will be needed (With a CPU 4 gigs or ram etc)

will a 800W Gigabyte Odin work with 2 9800GX2 in SLI + a new Quad core + a better mobo etc.

Cause i saw the 850W silverstone Strider in greece and it costs R1750 there and the Gigabyte Odin 800W costs R2000 along with the Coolermaster RealPower Pro Modular 850W. (R = Rand)

so will 50 watts make a differece in that setup?

how much will i need
 
At least a 1200w or better psu. Make sure you pay attention to the volts on the rails or rail, and it would help to get a known brand.
 
1200 watt plus for sli, i think the 800 would do you for the 1 gx2 but thats about it as far as power recommendations go
 
what!!!!!!!!!

never. in review sites thay say you can do one with a 500W but they recomend at least a 600W (the say system draw is about 400W)

1200W, well that does it i ain getting no GX2.

What about a 9800GTX rig?
 
You don't need 1200W, don't listen to those people. You actually only need 584W under full load, but to be on the safe side I would go with a 750W+ PSU, in case you decide to overclock or add more components.

I came to that conclusion using the Q9300, 2x DDR2 Modules, 2x 9800GX2's in SLI, 2 SATA Drives, 2x DVD-Burners, 4x 120mm fans, 1x PCI Card, and under 100% load.
 
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[-0MEGA-];948199 said:
You don't need 1200W, don't listen to those people. You actually only need 584W under full load, but to be on the safe side I would go with a 650-750W+ PSU, in case you decide to overclock or add more components.

I came to that conclusion using the Q9300, 2x DDR2 Modules, 2x 9800GX2's in SLI, 2 SATA Drives, 2x DVD-Burners, 4x 120mm fans, 1x PCI Card, and under 100% load.
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That's why I love Omega!
 
ChrisUlrich said:
That's why I love Omega!
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:D
fliegetn0.gif
 
[-0MEGA-];948199 said:
You don't need 1200W, don't listen to those people. You actually only need 584W under full load, but to be on the safe side I would go with a 650-750W+ PSU, in case you decide to overclock or add more components.

I came to that conclusion using the Q9300, 2x DDR2 Modules, 2x 9800GX2's in SLI, 2 SATA Drives, 2x DVD-Burners, 4x 120mm fans, 1x PCI Card, and under 100% load.
Click to expand...

if this is the case, then why do some people buy 1000W PSU's? that is way over the needed power
 
WhiteFireDragon said:
if this is the case, then why do some people buy 1000W PSU's? that is way over the needed power
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If people want a PSU that they can keep for a while without needing to upgrade, then buying a 1KW PSU may be a good choice for them. Some people also think the more power the better.
 
you guys in america are so lucky. Prices are sooo cheap

For example the 8800GTS is the same price as the GX2!!!!! the GT is just a little cheaper!!!

And power supplies a Gigabyte Odin 800W is $250

and a

Coolermaster Real Power Pro Modular 850W is $255

with the money i need here to build a "good" computer there i can make a super PC!!!!

Im probly gonna go with the Coolermaster. Will it be ok?

My rig is as follows

● Intel Core 2 Duo 2.13Ghz
● Biostar Tforce 965PT
● 1 gig ram
● ATI X1650 Pro 256MB
● Huntkey DH power 500w
● 2 80mm fans
● 2 hard drives
● 1 DVD burner/ drive
● Wi-Fi card

Ill upgreade over time to this

● Intel Q9300 Quad 2.5Ghz or better
● X38 or 780i SLI (SLI or CF)
● 2Gb Transcend AXE Ram 1066 4-4-4-12
● 9800GX2, 9800GTX or killer new ATI card (and dual up later)
● Power supply of need (ie. what will work )
● Coolermaster Centurion 590 with full deck of fans (ie. 7)
 
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Omega's approximation is a pretty accurate one. It's important to add an overhead to that, as it's never a good idea to run a PSU at close to 100% load. I wouldn't really want to go much below 800W, but either the Gigabyte or Coolermaster should do the job.
WhiteFireDragon said:
if this is the case, then why do some people buy 1000W PSU's? that is way over the needed power
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Add multiple processors, high end cooling equipment and/or large RAID arrays, etc... to that configuration and you'll actually be needing that sort of power. For people who aren't running those sort of systems a larger power supply will still perform better at lower loads. For example, if you had both a 500W PSU and 1000W PSU each capable of providing 5% voltage regulation and you loaded both to 500W, the 500W unit would be running at the far end of that 5% regulation range, whereas the larger PSU is designed to provide 5% regulation at 1000W, and so would be providing much tighter regulation at half its maximum loading.

Often it's done to allow overhead, upgradeability or bragging rights, though.


http://www.coolermaster.com/products/product.php?language=en&act=detail&tbcate=22&id=25 43

here is the site, its got 18 across 4 rails, and 28 over 2 = 6 rails at 128 amps (for some reason i dont think thats how its worked out at)
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It isn't. Underneath the amperage on each rail is printed the total wattage over all the +12V rails - 720W. Divide this by 12 gives you 60A, which is the total amperage over the +12V rails.
 
Im worried about this too. I have a 700w OCZ PSU and i hope its able to run my 9800gx2, q9450, 4 gb DDR3 and like 6 fans.
 
cchris1216 said:
At least a 1200w or better psu. Make sure you pay attention to the volts on the rails or rail, and it would help to get a known brand.
Click to expand...

He is basically correct, only thing i will add is that it depends on the PSU.

[-0MEGA-];948199 said:
You don't need 1200W, don't listen to those people. You actually only need 584W under full load, but to be on the safe side I would go with a 750W+ PSU, in case you decide to overclock or add more components.

I came to that conclusion using the Q9300, 2x DDR2 Modules, 2x 9800GX2's in SLI, 2 SATA Drives, 2x DVD-Burners, 4x 120mm fans, 1x PCI Card, and under 100% load.
Click to expand...


I am sorry, i cannot agree. Are you suggesting that 2 x 9800GX2 will be ok with a 750W psu? It depends on the PSU. Lets go with what nVidia say, and this is for 1 card not 2 -

http://www.nvidia.com/object/geforce_9800gx2_pwr_supply.html

Further considerations here: http://www.evga.com/articles/397.asp

ceewi1 said:
It isn't. Underneath the amperage on each rail is printed the total wattage over all the +12V rails - 720W. Divide this by 12 gives you 60A, which is the total amperage over the +12V rails.
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This is incorrect also, as under ATX design standards, 12V+2 is dedicated to the CPU, leaving the addition of the other rails for the rest of the system. Although the PSU is technically capable of delivering as you say, in practice it cannot due to the 240VA limitation. This is a key problem with "multi rail" PSU's.

I would suggest this: http://www.overclock3d.net/reviews.php?/power_supply/thermaltake_toughpower_1500w_w0171_atx_psu/1 which is essentially 2 x 750W psu's together. Let the flaming begin...
 
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bigfellla said:
I am sorry, i cannot agree. Are you suggesting that 2 x 9800GX2 will be ok with a 750W psu? It depends on the PSU. Lets go with what nVidia say, and this is for 1 card not 2 -

http://www.nvidia.com/object/geforce_9800gx2_pwr_supply.html

Further considerations here: http://www.evga.com/articles/397.asp
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The official recommendation for a single 9800GX2 is 580W with +12V@40A, which you can see quoted by a number of manufacturers. [H] measured a maximum power consumption of 594W from the wall, which corresponds to about 500W DC, even assuming a very high 85% efficiency on the PSU. I wouldn't want to go too much lower, but 1200W+ PSUs are not necessary.

This is incorrect also, as under ATX design standards, 12V+2 is dedicated to the CPU, leaving the addition of the other rails for the rest of the system. Although the PSU is technically capable of delivering as you say, in practice it cannot due to the 240VA limitation. This is a key problem with "multi rail" PSU's.
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Looking at the Coolermaster site again I can see it's actually 64A (768W). Even if 12V2 was completely unused, you'd still easily be able to deliver that 64A over the other rails (the sum of the OCP limits on the other rails is 110A, well above the 64A total limitation). While in some cases it's *possible* to exceed the OCP limitation on any single rail, in the overwhelming majority of cases for any well designed multi-rail PSU the total +12V limitation will be the limiting factor, not the OCP limit on any particular rail, as it would be on any single rail PSU.

I'm not saying that single-rail PSUs are bad, but for the average user it's a non-issue.

BTW, when two of the rails are rated at 28A, you're not looking at a PSU that's complying with the 240VA limitation :).
 
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