Hi, I have a Sapphire HD 7850 Oced edition, and was looking to add the exact same card to xFire it. My question is, do I need to plug in the power connectors into the GPU? I'm not good at computers, although I understand the basics, and I'm not sure whether my PSU has the extra cables I need to plug it in. Can I buy these cables?
I don't know, but I'll post what I found on the website for my PSU, thanks for your help
Compliance with the newest Intel standard ATX 12V V2.31
More than 70% efficiency under typical load operation
High reliability (MTBF > 100,000 hrs)
Green power design to meet Energy Star and Blue Angel requirements
Silent operation with intelligent fan speed control
Multiple protection design (OVP/OPP/OCP/SCP)
Supports dual +12V1 and +12V2 outputs for higher power usage
Model: PS-650TM (Intel Form Factor ATX 12V V2.31)
Input Voltage: 230Vac (180 ~ 264Vac)
Input Current: 4A at 230Vac
Input Frequency: 47 ~ 63 Hz
PFC: Passive PFC
Cooling Fan: 120mm Fan
Efficiency: > 70% Typically
MTBF: > 100,000 hrs
Max Output Power: 650W
Dimension (W x H x L): 150 x 86 x 140mm
Weight (N/G): 2.8kg
20+4Pin Motherboard: 1
4+4Pin+12V CPU: 1
6+2Pin PCI-E: 2
4Pin IDE: 3
4Pin Floppy: 1
Protection: OVP / OCP / OPP / SCP
Approvals: CCC, CB, TUV, CE, C-Tick
I hate to break it to you, but none of that points towards the 12V rail specification. The 7850's dont use that much power though. When you get a chance open the computer up and look at the label of the power supply if you can.
As long as the PSU has these connectors for all cards (you will need 2 total for CF to work), then you should be able to run the cards. You will need 2 6 pin PCI-E power connectors pictured on the left. Some PSU's have the 6+2 PCI-E connectors, those will work as well pictured on the right. I highly not recommend running CF even if you use the Molex to PCI-E adapters because of the 70% efficiency is not good for CF setups and your PSU won't deliver the full watts rating at full load.
I just did some digging around and your PSU only pushes max 550W at load which WILL NOT be enough for CF HD 7850's to safely operate since the OC'ed cards require more juice. This site says it runs only 550W max.
According to this review of your card, it drinks around 218W at load per card, that's around 438W for both cards, with your CPU being 100W and your mobo, HDD's, fans, CD/DVD drives using power, you will blow out your PSU and maybe burn out your entire computer, with your current PSU, I Highly recommend you upgrade your PSU to a more dependable PSU brand such as Corsair if you want to CF your card. Your PSU is a no name cheapo unit.
Thank you alot for your detailed explaination. Luckily I'm not planning to buy another card till around christmas, and you probably just saved my computer If i did buy another Card. What Psu do you recommend that stays within the $100 barrier and is good quality and efficient.
The Corsair TX 750 750W can be found for about $100 and it's one of the best in it's class. It should be a similar price in your country. You will have plenty of power and more importantly, dependability.