joanne said:
Hi all,
I have just purchased a gf 7950gt 512mb card to replace my 6600gt. Not only
is the new card much physically larger taking up 2 slots and longer to, it
also appears it needs a separate power supply to the card itself. The
dimensions should be ok if I rearrange my cards but I have no spare power
supply plugs.
The card comes with a square plug like the second one used on the
motherboard which splits into two plugs of the type used for hdd's and DVD
etc (please excuse my lake of technical knowledge). My system is as follows.
gigabyte K8 triton nf4 ddr400 mobo
amd 64 3200+
80gb hhd
120gb hhd
cd rom drive
dvdrw drive
floppy
1gb ddr400 ram
soundbaster 5.1 live sound card
case fan
atx tall tower (beige!!)
300w psu
What I need to know is,
Do I actually need 2 more plugs to just run this card?
If so will I need a new PSU or can you get adaptors?
If I need a new PSU how big would I need?
If my sound card gets in the way will the onboard sound be any good?
If I need an new PSU is it worth just buying a new case?
Thanks for any useful info
Andy
GeForce 7950GT 512MB
http://images10.newegg.com/NeweggImage/productimage/14-143-071-03.JPG
There is a 2x3 PCI Express power connector on that example card.
This page lists 30.76W through the slot connector, and 29.46W
through the 2x3 PCI Express power connector. That corresponds to
12V @ 2.56A on the slot connector, and 12V @ 2.46A on the PCI
Express 2x3 connector.
http://www.xbitlabs.com/articles/video/display/geforce7950gt_3.html
An S939 3200+ is about 67W from 12V. That is (67W/12V)*(1/0.90)=6.2A
http://www.amdcompare.com/us-en/desktop/details.aspx?opn=ADA3200DAA4BW
A hard drive draws 12V @ 0.6A while idle. You have two drives.
An optical drive has a boiler plate spec of 12V @ 1.5A. I actually
measured my CDROM the other day, and with the media spinning at max
speed, it measured 12V @ 1A. I would assume a typical usage pattern,
would be to use only one of the two optical drives at a time. So
when a person has two drives, I only count the power consumption on
one drive. (At least until someone can demonstrate a situation where
having two drives running at the same time makes sense. Maybe if
both drives are burners, I'd count both of them. But the power max
I usually calculate, is while 3D gaming, as that gives max video card
and processor power. Most people don't burn two DVDs while gaming
at the same time. My assumption of one optical drive running, is
to hold the game CD.)
For CPU fan, and the computer case fan, I allocate 0.5A from 12V fan
headers. Many fans have the actual rating printed on them, so you can
actually total these up for yourself.
If you had an old power supply, where there was a single 12V rail, then
the loading on that single rail is:
(2.56A + 2.46A) + 6.2A + (2 * 0.6A) + 1.5A + 0.5A = 14.42 amps.
If the supply has "12V1 12V2" designations on the label, it is an ATX
supply meeting spec 2.0+. The 12V2 is a separate output used to power
the processor. Your processor draws 6.2A from the 2x2 connector, and
that would come from 12V2. The 12V1 rail powers everything else. Using
the above totalling of amperes, the 12V1 would be 14.42 - 6.2 = 8.22A .
In terms of cabling, power supplies come in 20 pin and 24 pin versions.
The 20 pin connector only has a single wire to carry +12V motherboard
currents. The pin on the connector has a rating of 6 amps. Your
motherboard current flow is (2.56A + 0.5A) or the PCI Express video card
slot power, plus the fan header powers. This is well less than 6A,
so even if your motherboard has a 24 pin connector, you may safely use
a 20 pin connector with it if you want.
Since you did not list the output rating of the supply, I cannot finish
the analysis. If we take 12V * 14.42A, that is a power of 173W. Add to
that, about 50W for chips on the motherboard. That would be a total
of 223W or so. Still under the 300W total power limit. It would really
depend on the details printed on the label on the side of the
supply, as to whether you are getting too close to the limits.
This is an example of a good 350W supply. The idea here, is each output
has a high rating, and the only real limit on this supply, is the total
power numbers. Since your consumption is, say, 50W on the 3.3V/5V, that
is well under the 185W limit. And that leaves room thermally, for the
12V rail, to provide more of the allowed 350W total. Your total power
of 223W, would fit within the limits of this supply. Now, your 300W
supply, may be getting kinda close on the 12V single rail output, so
check the label and see if it has 14.42A plus a little margin (say
12V @ 17A). If it doesn't, you might want a different power supply.
http://images10.newegg.com/NeweggImage/productimage/17-103-455-02.JPG
If your power supply has enough amps on the 12V rail, then all you might
need is a disk drive to PCI Express power connector adapter. This
adapter is designed, so that two different disk drive cables, can
contribute power to a PCI Express 2x3 connector. Since your power
draw is so low on the 2x3 connector, only one disk drive cable needs
to be connected to the adapter. The other disk drive connector can be
left disconnected. The PCI Express end goes to your video card.
http://www.dealsonic.com/6inpciex2x4t.html
HTH,
Paul
