Re: PSU ATX 2.2 vs PCI E 2.0 specs
- From: Paul <nospam@xxxxxxxxxx>
- Date: Thu, 27 Sep 2007 18:33:01 -0400
jcazz wrote:
Greetings all,
I'm putting a new system together and want a PSU that can handle the demands of near future technology. Whats the difference between ATX 2.2 and PCI-E 2.0 spec. I'm thinking about either a Enermax Infiniti 720W or OCZ GameXtreme 850W. One claiming ATX 2.2 the the former touts PCI-E 2.0. The OCZ is cheaper, $140 US Clams including rebate. Enermax a cool $209 smacks. Not sure which one will be better for future tech... planning on upgrading Mobo, CPU, Ram and Video every nine months so want to get the most from PSU.
Specs are as follows:
MOBO - Asus MB with P35 or X38 chipset
CPU - Intel Q6600
Ram - DDR-3 2gig to start with
Video - Nvidia 8800 G? single for now
SCSI - Adaptec 2940 U2W
CD - Plextor UltraPlexWide
CDR - Plextor Plexwriter
DVD-HD+ Blue Sony?
HD's - 2X WD IDE
WD SATA
Lan - Duel Gig
Sound- Creative ?
Asus site recommends min 600w PSU
Thanks in advance
John
Formfactors.org is an Intel site, and the ATX spec is currently at version
2.2 . The spec defines a 24 pin main power connector. But the spec does not
define any PCI Express power connectors. They could be defined in PCI Express
specs from pcisig.org , but their specs cost money.
You can see examples of the connector types here. This supply has both 6 pin
and 8 pin PCI Express power connectors. If I'm interpreting the figure right,
the 8 pin PCI Express splits into two pieces, a 6 pin and 2 pin piece. Since
the 8 pin has (3) 12V power pins and (5) GND pins, I suspect the only new
function of the 8 pin connector, is presence detection. One of the extra GND
pins is used to detect that a connector is plugged in. In the case of the
8800GTX, that would be necessary so that the video card could tell that the
second connector is installed. (Leaving one guessing as to how they figure out
the first one is connected - unless they are sacrificing one pin on the 2x3 to
detect its presence also.)
http://www.pcpower.com/products/assets/T1KWSR/T1KWSR2.jpg
As to power rating, your major consumers are:
1) Q6600 (G0 stepping is 95W) (95W/12V) * (1/0.90) = 8.8 amps at 90% Vcore efficiency
2) 8800GTX - 10.6 amps through the main connector, a 6 pin and an 8 pin PCI Express
http://www.xbitlabs.com/articles/video/display/gf8800gtx-roundup_6.html
http://www.xbitlabs.com/images/video/gf8800gtx-roundup/8800gtx_full.gif
3) Three opticals. Three hard drives.
You can get a spec from the manufacturer for a hard drive. 12V @ 0.6A and 5V @ 1A approx.
Opticals vary. 12V @ 1.5A and 5V @ 1.5A used to be enough. The Blue Ray might
be a bit more. Optical 12V rail only draws current when media is present, and
my normal assumption is to assume only one optical is busy at a time (such as
when gaming). Not too many people would max their 8800GTX gaming, while burning
a bunch of CD/DVDs at the same time, but I suppose it could happen.
So I'll call this 12V @ 3A approx. And 5V @ 7.5A, 37.5W contribution to the
low voltage rails.
4) Fans add another 12V @ 0.5A, and the label on the fan will give more precise
numbers.
Total 12V current is 8.8+10.6+3+0.5 = 22.9 amps.
Total power 12*22.9 + 50W (motherboard 3.3/5) + 37.5W (storage 5V) + 10W (+5VSB) = 372.3W
An adequate supply would be one capable of providing the 22.9 amps on +12V
as well as meeting the total power requirement.
Connector wise, you'll need to buy a supply that has the right kind of
PCI Express connectors on it, for whatever you can realistically afford in
terms of video cards. Not all supplies will have a PCI Express six pin and
eight pin connector.
I would never buy an SLI configuration. I'd instead buy a single card, even
if it needed to be the 8800GTX or ultra. No point wasting another 130W of
power, for dubious gain. If you are running a "wall of monitors" (pushing a
lot more pixels), things might be different. Seeing as I have a 17" monitor,
one card would be plenty. YMMV.
Paul
.
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- PSU ATX 2.2 vs PCI E 2.0 specs
- From: jcazz
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