How do I know if my PSU supports SLI or CrossFireX?

[vchov]

I would like to build a system with these parts and would like to know how I'm going to power a two-card or three way SLI/CrossFire. The PSU has 2 6-pin PCIe connectors. One ASUS EAH5850 Radeon HD 5850 needs that many pins. Does that mean I can't run multiple GPUs, or is the power distributed through the cable the cards link to each other with? The parts I would like to use are here(Some prices are outdated, because of the sales):

Graphics Card: ASUS EAH5850 Radeon HD 5850 1GB PCIe x16($260)
http://www.newegg.com/Product/Product.aspx?Item=N82E16814121349

Motherboard: ASUS P6T LGA 1366 Intel X58 ATX Intel Motherboard ($240)
http://www.newegg.com/Product/Product.aspx?Item=N82E16813131359

Processor: Intel Core i7-920 Bloomfield 2.66GHz LGA 1336 Quad Core ($280)
http://www.newegg.com/Product/Product.aspx?Item=N82E16819115214

Case: Antec 300 Illusion Black Steel ATX Mid Tower($60)
http://www.newegg.com/Product/Product.aspx?Item=N82E16811129066

Power Supply: Antec TruePower New TP-750 Blue 750W($105)
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371022

Hard Disk Drive: SAMSUNG Spinpoint F3 HD103SJ 1TB 7200 RPM($80)
http://www.newegg.com/Product/Product.aspx?Item=N82E16822152185

Optical Drive: LITE-ON Black iHAS124-04 SATA($29)
http://www.newegg.com/Product/Product.aspx?Item=N82E16827151187

RAM: OCZ Platinum 6GB DDR3 1600 Triple Channel ($154)
http://www.newegg.com/Product/Product.aspx?Item=N82E16820227381

Wireless Card: D-Link DWA-556($80)
http://www.newegg.com/Product/Product.aspx?Item=N82E16833127218&Tpk=D-Link%20DWA-556

Ethernet Cable: Link Depot C6M-50-WHB 50 ft. Cat 6 White Network Cable($7.50)
http://www.newegg.com/Product/Product.aspx?Item=N82E16812189038

Thermal Compound: ZALMAN ZM - STG1 Thermal Compound($10)
http://www.newegg.com/Product/Product.aspx?Item=N82E16835118010

CPU Cooling Fan: COOLER MASTER Hyper 212 120mm($30)
http://www.newegg.com/Product/Product.aspx?Item=N82E16835103065

Anti-Static Wrist Strap: Rosewill RTK-002 Anti-Static($3.50)
http://www.newegg.com/Product/Product.aspx?Item=N82E16899261005

Operating System: Windows Vista Home Premium 64-bit OEM with Windows 7 Upgrade Coupon($110)
http://www.newegg.com/Product/Product.aspx?Item=N82E16832116677

Total Price: $1,439.00

 

[WR2]

The PSU has 2 6-pin PCIe connectors. One ASUS EAH5850 Radeon HD 5850 needs that many pins. Does that mean I can't run multiple GPUs, or is the power distributed through the cable the cards link to each other with?

That's an excellent PSU choice. You'll want to plug 1 of the PCI-e power cables into each video card.

For the 2nd power cable you'll use the Molex-to-PCI-e adapter you'll find in the video card accesory kit.

Left side of the picture, just under the EAH label on the box.

 

[jbakerlent]

Doesn't that PSU have four 6 pin PCI-e connectors?

 

[WR2]

You're right - there are 4x PCI-e connectors (2x6pin and 2x 6+2pin).
He's good to go.

 

[jbakerlent]

Also, since you mentioned the possibility of 3-way crossfire, first of all you could use WR2's method to power the third card, however you would be cutting it a little close and also not getting much benefit since the third slot would only be operating at x4.

 

[vchov]

Thanks a lot! This was very helpful. As for using a 3-Way CrossFire, and "cutting it a little close", I assume a PSU with more watts would fix that? Perhaps an 850W?

 

[WR2]

750W Antec TruePower New TP-750 has enough power for 3x 5850s
Two 5850s in CrossfireX will use something under 500W on your system.
A 3rd 5850 will push that near 650W.

 

[vchov]

Oh, okay. Thank you again. Now I just need to wait for the card to be back in stock at Newegg.