Do I need to plug in power cables into a second card?

[JJ1217]

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?

 

[Deemo13]

What PSU do you have?

And yes you would also have to plug in those cables. They can be bought, but I wouldnt recommend it.

 

[JJ1217]

I have a Widetech 650 W. It's not the best brand, but I've used them for years and never had a problem.

 

[Deemo13]

How many amps do you have on the 12V rail? I just googled it and it stated that it gets around 70% efficiency.

 

[JJ1217]

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

and



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
SATA: 4
4Pin IDE: 3
4Pin Floppy: 1
Protection: OVP / OCP / OPP / SCP
Approvals: CCC, CB, TUV, CE, C-Tick

 

[Deemo13]

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.

 

[El Tigre]

I honestly would recommend a better PSU such as Corsair for example. You will also need to connect the PCI-E power connectors on all cards for CF to work.

 

[JJ1217]

Ok, say I open my computer, which isn't hard, where do I look for the 12V rail thing? I don't know what exactly to look for. Im pretty sure 650 W is enough for two 7850's.

And El Tigre the efficiency of my PSU is decent enough, and I've used their brand lots before and they are trustworthy. They even have their own Australian website, so that suits me even better.

 

[El Tigre]

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.

*CORRECTION*


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.

http://www.jw.com.au/widetech-650w-silent-psu-120mm-fan-support-pci-ex-p-674

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.

http://www.neoseeker.com/Articles/Hardware/Reviews/Sapphire_HD_7850_OC/14.html

 

[JJ1217]

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.

 

[El Tigre]

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.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817139021&Tpk=Corsair%20750

 

[JJ1217]

Cheers. Its available for around $140 at mwave.

 

[El Tigre]

I would still suggest saving up for it, it's really worth it.

 

[JJ1217]

Best answer selected by JJ1217.

 

[JJ1217]

uhm, sorry to bring up this thread so late, but just want to check what are your recommended PSU's to get.

Theres the TX 750,

then theres also this for $69
http://www.msy.com.au/product.jsp?productId=4917

this
http://www.msy.com.au/product.jsp?productId=4992

and this
http://www.msy.com.au/product.jsp?productId=7999

What do you recommend? The Asus one looks good, 80% efficiency, but I'm not sure how to check if It has the cables I need, also for the motherboard and stuff. Do you know how to check it.?