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PSU for Quad 5850, i7 980, 16GB DDR3 1600

N

Net

Golden Member
I have:

i7 980 @ 4Ghz
2x 5850 @ 850/1200
16GB DDR3
850 psu

would a 850 psu support a quad 5850? edit: won't be using quadfire. these will be run for non-gamming, number crunching type of work

what if I run quad 5850? two will be at 850/1200, the other two probably 825/1200. Do I need to drop my i7 overclock or other overclocks?

edit: will be down clocking memory to lowest possible. the 5850s actually perform really well for the type of work i'm doing, better then 6870s do. specifically targeting 5850s for $/performance.
 
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Why would you run quad 5850? You'd be limited by 1GB VRAM and diminishing returns per card. If you want increased performance, sell your 5850's and buy dual GTX 670's, or 7850 2GB trifire, or something like that. These will run on your 850W PSU. What's your gaming resolution? Triple monitor?

5850 quadfire requires eight 6-pin PCIe connectors. Not even top grade 1000W units have those (although they'd handle it). To have 8 PCIe connectors out of the box you'd need Enermax MaxRevo 1350W or similar
 
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lehtv said:
Why would you run quad 5850? You'd be limited by 1GB VRAM and diminishing returns per card. If you want increased performance, sell your 5850's and buy dual GTX 670's, or 7850 2GB trifire, or something like that. These will run on your 850W PSU. What's your gaming resolution? Triple monitor?

5850 quadfire requires eight 6-pin PCIe connectors. Not even top grade 1000W units have those (although they'd handle it). To have 8 PCIe connectors out of the box you'd need Enermax MaxRevo 1350W or similar
Click to expand...

I'm running them for non-gaming number crunching type of work. I won't be using quadfire. I'll update my post.

I have a corsair 850TX. looks like it only has 4x PCI-E connectors 🙁

assuming that i had the connectors then, If I don't use quadfire will I be okay to overclock everything and have ? I can drop the i7 980 down to stock if needed.
 
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edited Not sure how power consumption changes with using the cards for computing without quadfire, I have no idea what that entails sorry.

Regardless, your PSU doesn't have nearly enough connectors.
 
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lehtv said:
edited Not sure how power consumption changes with using the cards for computing without quadfire, I have no idea what that entails sorry.

Regardless, your PSU doesn't have nearly enough connectors.
Click to expand...

looks like I'm back in the game. Did some research and saw others doing the same type of work I am using 4pin molex to 6pin PCIe connectors for the power.

the only question now is if the power can handle 4x 5850 at 100% load and an i7 980.
 
If all 5850's will be at full load simultaneously, that's about 150W per card at stock. With the 15-20% overclock you're planning, over 700W combined. Even more if there's you're increasing volts. Add the rest of your components and you're exceeding the rated wattage of your PSU, and as a rule of thumb you should stay under 80% of the rated wattage to be safe in the long term. There's a reason an 850W power supply doesn't have 8 PCIe connectors. You'll need a new PSU
 
lehtv said:
If all 5850's will be at full load simultaneously, that's about 150W per card at stock. With the 15-20% overclock you're planning, over 700W combined. Even more if there's you're increasing volts. Add the rest of your components and you're exceeding the rated wattage of your PSU, and as a rule of thumb you should stay under 80% of the rated wattage to be safe in the long term. There's a reason an 850W power supply doesn't have 8 PCIe connectors. You'll need a new PSU
Click to expand...

this one has 8 connectors and is 850W http://www.newegg.com/Product/Produc...82E16817104143

if I'm overclocking then maybe i'll just want to stick with 3 cards?
 
You could dual PSU it if you don't care about looks. Snag a decent 650 watt psu or so to supplement and you'll be fine. Power two of the 5850s with the 650 watt and the rest of the machine with the 850.
 
Net said:
this one has 8 connectors and is 850W http://www.newegg.com/Product/Produc...82E16817104143
Click to expand...

Sure, there are exceptions to every rule. It doesn't mean you should be running 4x5850 at full load on that PSU any more than your current unit.

if I'm overclocking then maybe i'll just want to stick with 3 cards?
Click to expand...
It'd still be pushing it at full load with those overclocks.

3 * 150W (gpu) * 1.2 (oc) + ~200W (the rest) = 740W, or 87% of the rated wattage. Not recommended. Lower your i7 volts and clocks, and stick to 10% OC on the GPUs and you should be fine
 
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OVerLoRDI said:
You could dual PSU it if you don't care about looks. Snag a decent 650 watt psu or so to supplement and you'll be fine. Power two of the 5850s with the 650 watt and the rest of the machine with the 850.
Click to expand...

Would need some way to power up the secondary PSU e.g. by joining the ATX 24-pin cables or jumpstarting it with the paperclip method... Much simpler to just sell the 5850's and upgrade, or sell the 850W and upgrade
 
My Kingwin Lazer 1000w 80+ Gold only has 6 connectors, but I'm sure another card would run of adaptors.

I do agree though, Quadfire with 5850's @ 1GB is going to really limit the performance. Even tri-fire is going to bottleneck due to low vram. Ideally you'd want 3GB or 4GB cards for quad fire.

Sell the 5850's at $125 a pop, and buy a 670.

SLI it down the road. Way less hassle, way better minimums.... not memory restricted.

I imagine 4 5850's isn't going to run anymore than 30% faster, while minimums will probably be lower than a single 670. But Im just guessing.

EDIT- I don't think the 680 is worth $100 more than the 670, but if you want the 680, go for it.
 
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updated post to give more background. memory doesn't matter to me. also i'll down clock the memory speed as low as possible.
 
If you're decided on using 5850's, you have two choices: 3x 5850 with your existing PSU and lower overclocks than planned, which would push the limits a bit but would work. Or 4x 5850 with this PSU or this; they are the cheapest good quality units that have eight PCIe connectors.
 
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