2 x 8800 Ultra in SLI....What PSU wattage is needed

I am think of getting 2 x 8800 ultra's in SLI...What PSU wattage is needed.

Will also run with a quad processor, so will 1010Wattage be enough for my
needs.

Thx

"Leigh-Anne" wrote in message

I am think of getting 2 x 8800 ultra's in SLI...What PSU wattage is
needed.

12v ampage matters, not PSU wattage. In this case, approximately 25A for
the cards alone.

Will also run with a quad processor, so will 1010Wattage be enough
for my needs.

Twin 8800GTXs with an Intel Kensington quad-core have been shown to run on a
decent 500W PSU. It's nice to have a bit of headroom but that's just
ridiculous.

Leigh-Anne wrote:
I am think of getting 2 x 8800 ultra's in SLI...What PSU wattage is needed.

Will also run with a quad processor, so will 1010Wattage be enough for my
needs.

Thx


QX6850 3GHZ/FSB1333/8MB L2 130W/12V * (1/0.90) = 12 amps at 90% Vcore efficiency
http://processorfinder.intel.com/det...px?sSpec=SLAFN

The 8800GTX is listed as 131.5W measured, at the bottom of this page. I
cannot find a measurement for the 8800Ultra - Xbitlabs claims the card wouldn't
run properly on the testbed they use for power measurement. (They add current
shunts to the power rails, to allow measuring them.)

http://www.xbitlabs.com/articles/vid...roundup_6.html

The clocks are listed here, for a couple cards. The Ultra is only a hair faster.

# Nvidia GeForce 8800 Ultra (G80, 612/1512/2160MHz, 128sp, 32tmu, 24rop, 384-bit, 768MB)
# Nvidia GeForce 8800 GTX (G80, 576/1350/1900MHz, 128sp, 32tmu, 24rop, 384-bit, 768MB)
(Core/Shader/Memory)

A guesstimate would be 10% more power, say 144W for the Ultra, or 12V @ 12A.

So 36A for processor and two graphics cards, another 3 or 4 amps for basic disk,
CDROM, cooling fans, yields about 40A from the 12V rail. Allocate 50W for
motherboard power and RAM, 10W for +5VSB, throw in a little extra if the RAM
is being overclocked - 480 + ~100W = 580W.

This Silencer 750W should be enough and it has the connectors.
http://www.pcpower.com/products/view...view=techspecs

It is funny that the list here, on Slizone, starts at 900W for dual Ultras.
http://www.slizone.com/object/slizone_build_psu.html

This site does power supply reviews, and clicking the "Next" at the bottom,
will go through the list of 58 supplies they've reviewed. The largest one
I see listed so far, is a 1200W unit.

http://www.jonnyguru.com/reviews.php?catID=1

The PCPowerandcooling designs are single output rail. Some of the other big
supplies use more than one output circuit. In the past, this was only an
issue, if any of the 12V outputs had a restrictive rating, such that you had
problems getting enough current for single large loads. I'd prefer to see
the six pin and eight pin for powering the 8800 Ultra, come from one rail,
but the table here seems to mix the connectors across the various rails.

http://www.jonnyguru.com/review_deta...111&page_num=2

The picture here is much clearer. This is for the modular cabled version of
the same supply. You'd use the upper right two red connectors for one
video card, and the lower left two red connectors for the other card.
With the PCpowerandcooling, you'd just hook them up and not worry about it,
since they're all on the same output.

http://www.jonnyguru.com/PSU/Toughpo...W/DSC01276.JPG

Part of the selection process should also include considering the
efficiency rating of the supply. At this power level, you want something
in the "80+" efficiency category, and actually, to even be able to build a
supply this big, requires efficient circuits (Seasonic was the first,
with their "forward converters"). I saw a figure of 87% in one of the
JonnyGuru reviews, which is quite amazing. The reason this is
important, is because it minimizes the heat the power supply itself
kicks out. That allows the big fan on the supply to spin slowly,
and still keep the supply cool.

Have fun shopping, and try and find some reviews of the product you plan
to purchase, to learn more about it.

Paul

On Sep 28, 1:57 pm, "Leigh-Anne" wrote:
I am think of getting 2 x 8800 ultra's in SLI...What PSU wattage is needed.

Will also run with a quad processor, so will 1010Wattage be enough for my
needs.

Thx

I ran two 8800 GTX's on a 550Watt supply for about a month without any
problems. The CPU is an E6600 Oc'ed to 3ghz.

Matt

Here's a power supply calculator.. 'Power Supply Calculator'
(http://www.journeysystems.com/power_...calculator.php)

davy

davy wrote:
Here's a power supply calculator.. 'Power Supply Calculator'
(http://www.journeysystems.com/power_...calculator.php)

Its device list is a bit out of sync with time..

--
@~@ Might, Courage, Vision, SINCERITY.
/ v \ Simplicity is Beauty! May the Force and Farce be with you!
/( _ )\ (Xubuntu 7.04) Linux 2.6.22.8
^ ^ 21:50:01 up 4 days 40 min 1 user load average: 0.03 0.08 0.03
news://news.3home.net news://news.hkpcug.org news://news.newsgroup.com.hk

Worthless. By the looks of it, It's about 3 years old.
It would be a great site if the list was updated.

Good find!

"davy" wrote in message
...

Here's a power supply calculator.. 'Power Supply Calculator'
(http://www.journeysystems.com/power_...calculator.php)

davy