Is it safe to to run x1900xt on a 400w PSU?

[Mithrandir]

Please see THIS thread regarding a query from AgentK.
Personally I don't reckon it's safe to run it!

[amjedm]

I think his 400W psu should be ok if it is the AOpen psu he lists in his system spec (and if is made by FSP/Fortron).

Bloke in this thread (http://www.silentpcreview.com/forums...ower&start=180) is running

CPU: e6400
MB: Gigabyte DS3
GPU: BFG7900GT
RAM: Team PC2-6400

on a 300 watt psu (20amp on 12v rail) And both CPU/GPU are overclocked. No problems yet.

Have a look at the rest of the thread posted above about what's being powered from a 300 watt psu.

[kalniel]

Wattage isn't the problem here, but Amperage on the 12v line can be with this card.

My guess would be that if it's a single rail PSU it'll be fine, but if it's a dual rail and you've got low A on the rails then it's not so good.

[problemo]

A dual rail 12V PSU should be used, with at least 20A on one of the rails, so something like Seasonic S-12 430W or better...

[kalniel]

Why do you think dual rail is better? I believe the opposite at this power range (400W or lower).

[Flewis]

The opposite is true, when your psu is only about matching the required power having dual rails usually ends up wasting power by not fully utilising one rail and over utilising another giving instability. If all the power is on one rail no power is wasted and the maximum output for the psu can be achieved.

[TarnxTarn]

It does not matter if it is dual rail or single rail... as long as the PSU can produce enough current (Amp) with stable voltage(12V)... they are good to go...

[Agent]

Why do you think dual rail is better? I believe the opposite at this power range (400W or lower).

Agreed. At this level its a bit unusual to use a dual rail.

It does not matter if it is dual rail or single rail... as long as the PSU can produce enough current (Amp) with stable voltage(12V)... they are good to go...

In this case, it would matter.
Its unlikely a PSU @ 400watt be able to supply enough amp's on both rails for the graphics card and the rest of the system (hes running a P4 prescott for a start )

Otherwise I agree - Provided the rails can supply enough amps to the parts they are powering it makes little difference in todays systems. Dual rails are a better option in theory, and I think they will come into their own in time (Although by how much is debatable)

The opposite is true, when your psu is only about matching the required power having dual rails usually ends up wasting power by not fully utilising one rail and over utilising another giving instability. If all the power is on one rail no power is wasted and the maximum output for the psu can be achieved.

Dual rails isnt about saving wasted power though - its about keeping noise down and stable voltages, on the rails due to today's insanely powerful parts.

Buying an under-rated dual rail PSU is no different to buying an under rated single rail. Research needs to be done before hand - Just because its dual rail, it doesn't change that

[redddraggon]

I ran a 8800GTS off a 400W FSP and it didn't suffer. Is the GTS a higher power consumer than the x1900xt?

[Agent]

I ran a 8800GTS off a 400W FSP and it didn't suffer. Is the GTS a higher power consumer than the x1900xt?

Wattage means *nothing*

Its all about the amps it can supply

Just to make things clear - you shouldn't ever damage the card by using a PSU which cant power it. It just wont work / have stability issues / trip the PSU.

[Mithrandir]

I ran a 8800GTS off a 400W FSP and it didn't suffer. Is the GTS a higher power consumer than the x1900xt?

It's not so much about the wattage as mentioned above, the x1900xt needs 30a whereas the 8800 gts requires 26a from my understanding.
Most 400w PSUs don't have 30a on the 12v rail if I'm correct.

[kalniel]

Unless they're single rail ones.. in which case they almost always do

If the choice is between a single rail 30a 12v line, and a dual rail with 15a on each rail.. the single rail will run the x1900xt and the dual will really struggle

Dual rails were really designed for keeping the supply to the CPU seperate from the supply to the hard drives and other components.. and it was arguably more important back in the days of the p4 when we had very hungry CPU designs. So it's nothing to do with power unfortunately, and to provide the same power to a graphics card you usually need a much more powerful dual rail than you would a single, and no thanks to a silly ATX specifications that 'limited' each rail to 18a dual rails are best avoided in several cases.

[Mithrandir]

Unless they're single rail ones.. in which case they almost always do

If the choice is between a single rail 30a 12v line, and a dual rail with 15a on each rail.. the single rail will run the x1900xt and the dual will really struggle

Glad my PSU has a single rail then (33a)
I would be sure my x1900 would have struggled otherwise. (Though I'm certain its just managing on my PSU)