What happens when Psu isnt enough

[Guest]

Hello,
i just got a 9800gtx + from nvidia, they replaced my old 8800 with the before mention 9800gtx, i was looking at its power requirements, it needs 450w minimum, my psu supplies 450w maximum, with this new graphics card and fully updated drivers my computer is considerably slower, is this a PSU problem?

 

[Guest]

it tells me that i dont have enoughh power when turning on my computer, but going from 40 fps on max graphics with old card to 20 fps on minimum graphics with the 9800gtx+, could there be a problem with gpu or is the PSU capable of this?

 

[13thmonkey]

have you plugged in the extra power cables to the gpu?

typically when the psu is being stressed beyond what it can do the system will become unstable, the psu will eventually and suddenly die, and may damage other components.

the psu is essentially dumb and will just keep supplying power till it gives up (often as a result of overheating), the gpu cannot know that the psu is getting close to the edge, hence why i think that its just not been fuly plumbed in.

 

[jsc]

Could be either. One of the usual symptoms of an inadequate PSU is a reset/reboot cycle under heavy 3D load.

Can you test the 9800 in another system to make sure it is good?

 

[Guest]

the card has 2 sockets but my psu only has one power clip for it :S i can test it in another system but it will be awkward as the only other system available is put together very tightly :S

 

[Guest]

i will check it in the other system if its ok to do so and ill have a look at the wiring

 

[13thmonkey]

you need to plug both in, get a converter from molex to pci-e

 

[13thmonkey]

the two plugs are not optional by the way, I had a 6600GT that i didn't plug the single power adaptor into and it also warned me about low power. your card is fine. No need to break into your other system.

 

[Guest]

should i get a new PSU then? since mine only has one power cable for graphic cards

 

[13thmonkey]

molex to pci-e convertor should be fine. fyi my Q9550 + 8800GTX only draws approx 280W max, 12V amps are more important than watts.

 

[Guest]

I was taking a look around my system after i got a molex to pci-e convertor and found that my psu doesnt have any more molex slot thingies available. my psu has 12v rating of of 20 A does this 20 amps matter because it seems most cards need more than 20 A

 

[13thmonkey]

I think your card suggests 24amps? you could try it, but i'd put money on your psu burning out fairly quickly and probably taking everything with it.

 

[Guest]

I had alook at the voltage reading for each rail on my psu
the3.3v rail read something like 3.31v
5v read something like 5v
but the 12v rail only read 1.68
my old graphics card died unexpectedly

does this show that my psu is kinda dead or that it killed my last gpu?

 

[rodney_ws]

http://www.corsair.com/cinema/movie.aspx?id=622747

 

[13thmonkey]

if you truly had 1.68V on your 12V rail your pc wouldn't be working, can you read the voltage in bios? its probably a reading error which isn't that unusual.

as rodney has hinted at, PSU's are a vital foundation, don't skimp on them. It does sound like you need a new one as its doesn't have the oomph for your new card, i'm surprised its not already failed to be honest.