I'm Soon building another computer and i wish to put a 4870 into it BUT down the road i am goin to put another 4870 in it.
i need some suggestions for a Power Suply i was going to get a ThermalTake Tought Power 750Watt but i read some reviews that they well SUCK! and can't preduce the power they require. i would like to buy from this web site http://www.msy.com.au/Parts/PARTS.pdf. Thank you again BTW i have a tight budget so thanks in advance.
Its not the power.. its the pci-e 6+2 connectors. A 4870 crossfire will consume less than 600watts. A 4870x2 crossfire consumes less than 850, so a 750 should be fine.
I recommend the corsair 750 or the PC Power &Cooling if you want to go down the 750watt road. Just look at the 12v. Rail. Anything above 20A should suit your needs.
I'm using the TT Toughpower on 1 rig and the Corsair on the other - no problems at all. I'm also running crossfire.
The Tough 750 has 4 x 12v rails with 18amps each for a "combined loading of 56amps" (18 * 4 = 72amps but at 80% efficiency...).
I read some benchmarks saying the 4870 peaked at 250 (one site said 290) watts during heavy gaming. Based on amps = watts/volts (12v rail), its a draw of 20.8 to 24 amps under that load. That means if you want to ensure you can power your card you need to supply it with at least 24 amps.
2 x 12amp rails won't work cause it'll only use 1 rail so it'll see only 12a. So a 4 x 18amp power supply will only deliver 18a, 6amps short of your need.
Since you want to have two of these cards you'll need at least 2 x 24amp v12 rails or a single 48amp v12 rail. Your CPU/mb/drives require power also so you'll have to accommodate them too. I'd suggest getting either a single 12v rail psu or a dual 12v rail psu.
On my desktop I use two power supplies. My bigger power supply runs my vid card and motherboard. The smaller ones runs all my drives and fans. To do it I connected the signal on pins with a mouse cable so they work in tandem. With this method I got the power I needed but only one power supply has all its pins connected to the motherboard so only that one can report back any useful info on it's power situation. Doesn't bother me. I'd prefer my psu didn't talk to my motherboard