is 850w enough for crossfire gaming rig?

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sillyputty

I'm building a new gaming rig and got an Antec TPQ-850 850w ATX12V /
EPS12V SLI certified crossfire ready PSU. I was reading the mobo (asus
P6T-deluxe X58 w/Intel i7 940) instruction manual and it recommends a
1000w PSU when running two, or more, 'high end' video cards. I have
two VGA SAPPHIRE HD4850s that I'm planning to run in crossfire. I also
be installing 2 Seagate Barracuda ST3500320NS 500g HDs in RAID 0. The
case is Antec 900 with three fans (I may add more or go with water
cooling). I checked the average power usage (watts) of all the current
components and the total was well within 850w.

Is that enough to run my rig? Thx.
 
sillyputty said:
I'm building a new gaming rig and got an Antec TPQ-850 850w ATX12V /
EPS12V SLI certified crossfire ready PSU. I was reading the mobo (asus
P6T-deluxe X58 w/Intel i7 940) instruction manual and it recommends a
1000w PSU when running two, or more, 'high end' video cards. I have
two VGA SAPPHIRE HD4850s that I'm planning to run in crossfire. I also
be installing 2 Seagate Barracuda ST3500320NS 500g HDs in RAID 0. The
case is Antec 900 with three fans (I may add more or go with water
cooling). I checked the average power usage (watts) of all the current
components and the total was well within 850w.

Is that enough to run my rig? Thx.
Click to expand...

A couple 4850's were measured here. 115W each. So two is 230W.

http://www.xbitlabs.com/articles/video/display/sapphire-toxic-hd4850_5.html#sect0

The i7-940 is listed as 130W. The designs are equipped with power
limiters (throttle the CPU when power consumption goes over a
certain level), but that function can be disabled. I don't know
whether the power limiting function allows it to go to the
TDP value or not. Scaling for estimated Vcore efficiency of 90%, the
input to the CPU is 130/0.90 = 144 watts to create 130W for
the processor to use.

http://processorfinder.intel.com/details.aspx?sSpec=SLBCK

Two disks at 12W each, CDROM at 25W (when media present), 10W fans,
10W standby, 50W chipset/RAM power, is another 119W. (Some hard
drives are now drawing less than my boilerplate value now.)

Total so far, in watts, 230+144+119 = 493 Watts

And that represents an upper limit. It is possible, while in
Crossfire, that the two cards don't run at full power. In game
play, not all cores will be pushed to the wall. (Running something
like Prime95, might make getting to the power limit, easier.)
Compute loads while gaming are not necessarily symmetric.

Antec TPQ-850 850W
+3.3V @ 25A, +5V @ 30A, -12V @ 0.5A, +5VSB @ 3.0A
+12V1 @ 18A, +12V2 @ 18A, +12V3 @ 18A, +12V4 @ 18A
768W max total on combined 12V rails, or 64 amps spread out
180W max combined for 3.3/5V

Wiring plan is explained here. Your 24 pin uses 12V @ 6A plus
the current for the CPU fan. The 2x3 PCI connector on each video
card is 12V @ 6.5A. The processor power connector would be using
up to 12A. You should attempt to use the PCI Express connectors
that aren't sharing with some other high load (if you can figure
out which is which).

http://www.jonnyguru.com/modules.php?name=NDReviews&file=print&reid=58

Paul
 
sillyputty said:
I'm building a new gaming rig and got an Antec TPQ-850 850w ATX12V /
EPS12V SLI certified crossfire ready PSU. I was reading the mobo (asus
P6T-deluxe X58 w/Intel i7 940) instruction manual and it recommends a
1000w PSU when running two, or more, 'high end' video cards. I have
two VGA SAPPHIRE HD4850s that I'm planning to run in crossfire. I also
be installing 2 Seagate Barracuda ST3500320NS 500g HDs in RAID 0. The
case is Antec 900 with three fans (I may add more or go with water
cooling). I checked the average power usage (watts) of all the current
components and the total was well within 850w.

Is that enough to run my rig? Thx.
Click to expand...

You need a 700-800W power supply. I don't know why asus would recommend a
1000W power supply. Maybe they were thinking you might go with a no-name
1000W unit that can really only handle ~700W? -Dave
 
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