I'm planning a computer build and had a question about power requirements. I was going to get two GPUs, and they both require 500 watts each. Sounds like a silly question, but would this mean I'd need a PSU larger than 1000 watts to power the whole deal? Someone told me about their build and how they used two graphics cards, both needing 500 watts, and only had a 1000 watt power supply. Wouldn't you need more than a 1000 to power both the cards and the CPU and everything else? I'm just a tad confused here, and any help would be greatly appreciated.
The wattage requirements are for the system as a whole, the 500 W recommendation includes the power needed for the CPU, motherboard, hard drives, and other components, so when you add in a second card you dont need to double the recommended power, you just need to add a bit more than the power consumption for that card. A good 750 W PSU will power most dual card setups, an 850 W power supply can power almost any dual card setup.
Thank you all for your replies, and I apologize, I guess it would've been easier for me to have just told you which cards I was getting. The cards I'm looking at are two Radeon HD 6950s. To be more specific, this one here:
A 6950 draws about 200W of power at peak load, two of them will be pulling 400 W from the power supply, another 150 W for the CPU, 100 W for the motherboard and assorted peripherals puts you at about 650 W so a good 750 W power supply with about 60 A of current available to its 12 V rails will be plenty for that setup, definitely no need for a 1kW unit.
I know my math is kinda fudgy, but its fudged high to be on the safer side, a quick run through on the PSU calc comes to about 600W so my rough math is pretty close.
I just used the power supply calculator, and I already have a PSU powerful enough to run my setup. Thank you for that suggestion, Gamer-girl! I think I have all the info I need, so thank you all for your time!
Unfortunately no, the LSP 750 has a single 12 V rail that is only capable of providing 45 A(540 W) at most, and since the two GPUs and the CPU will need about that much that means you run the risk of overloading the unit when under full load since anything with a motor is also drawing some power from the 12 V rail.
Ultra units aren't great, they don't have quite as much power on the 12 V rail as you would like to see in a modern unit where 80% of your power used is from that rail. It might work, but it would be really close, and if that unit is more than a few years old it is less likely to be able to do it.
The sites will display the information differently. Some will have it in the wall of text about the power supply, others will be included in the details sections.
But usually it will have +12v then a number like 62A. This is usually the output of a quality 750w power supply. Also since you are shopping for a new power supply you might want to get a 80 plus unit with at least 4x 6-pin PCI-E connectors.
Some quality brands are antec, corsair, seasonic and XFX.
Yes that is what you will need. They are typically 6-pin but some higher end card will use a combination of a 6pin and 8pin per card.
The HX850 has 4x 6+2pin which means the connector can be used as a 6pin or if you add on the extra 2 pins it will function as a 8pin. A bit like how the big 24pin power supply cable can be separated into a 20pin with an extra 4pin.
Alrighty. So this one will work? It says 8/6 pin rather than 6+2... could it still be used? On the diagram on the Tiger Direct page, it looks like the PCI-E connector is one whole 8-pin connection, so I wasn't sure how that would work with a 6-pin. I just wanted to be clear.