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850W PSU not enough for an 8800GTX?

Teal

Teal

Teal

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Joined
2 Dec 2002
Posts
1,611
Getting the 'not enough power' warning from BFG8800GTX.

The PSU is an Antec TruePower Quattro 850W and yes I've got two PCI-E connectors plugged into the 8800.

The PSU comes with 4 PCI-E connectors and it doesn't seem to matter which pair I use, either the modular ones or the fixed ones or even one of each, still the card complains about not enough power.

Any thoughts?
 
Sounds like a dodgy PCI-E PWR connector to me, try another one. Or try switching them round etc. That PSU is more than enough.
 
I've run one off a 550W PSU. Try not using the PCI-E dedicated leads, but use molex to PCI-E converters from a couple of other power leads.

Also, have you tried the card in another machine?


M
 
yeah 850 watt, plus its a good named brand, means you have PLENTY of head room. you probably barely use 400-500 watts tbh.

as another person suggested, use some molex-pci-e instead to see if its any different.
 
Nothing excessive in the rest of the system, it is in an Antec Nine Hundred case so that has 4 fans.

2 x 150GB Raptor and a single DVD writer.

Only other card is a PCI-E X-Fi card.

Nothing there that should be causing any problems at all.

I've already swapped around different combinations of the 4 PCI-E power connectors and I can try using molex to PCI-E but I'm probably left with either a faulty graphics card or a faulty PSU.

I'll swap the graphics card to another PC I have here with a 700W PSU, that should help determine if it is the PSU or the card.
 
The GTX worked fine in the other PC with a 700W PSU.

Also the GTS from that one worked fine with the 850W PSU in the original PC.

I also tested each individual PCI-E power line with the GTS and it was fine with any of them.

Using Molex to PCI-E connectors made no difference either.

Ah well, next step is to switch the PSUs between the PC's and see what difference that makes.

All very strange
 
Switched the PSU's and the GTX runs fine along with the other hardware in the new PC on the 700W PSU.

No surprise there really.

The 850W Antec runs the GTS in the older PC quite happily so I thought I'd swap the GTX back in to see if it was any better with that PSU in a PC with only a single HDD but same as before, 'insufficient power'.

So it seems I have an 850W PSU that can't power an 8800GTX.

Looks like I'm in RMA territory.
 
Its all about the 12V rails combined output. I have a 460W Zalman silent PSU with only 34A but this is more than enough for an 8800GTX + Intel QX6850 as well as several HD & DVD drives.
 
The Antec has way more than enough combined output in theory, it is intended for SLi use after all, hence the 4 x PCI-E connectors so it remains a mystery why it would struggle to power a single GTX.
 
The conclusion jonnyguru came to in his review of the quattro:

Rail Wire Color Connector
+12V1 Y/Blk 4-pin ATX12V and 8-pin EPS12V
+12V2 Yellow All Peripherals
+12V3 Y/Blue Main 20+4-pin, 1st modular PCI-e, one of the fixed PCI-e connectors
+12V4 Y/Green 2nd modular PCI-e, one of the fixed PCI-e connectors

Now each of those rails is individually specced for 18A, but combined they give 64A (or 16A each). From my reading of the above table, ideally you want both pci-express connectors to be drawing from the 4th rail (not fighting with your motherboard for power on the 3rd rail). I think there must be 4 permutations of fixed and modular that can be tried of which 1 will achieve that. But if the BFG still reports not enough power in all 4 scenarios, that'd be me stumped.
 
I did try all the combinations, but even if that worked it wouldn't let you run SLI as you'd still need all 4 to work.

There has got to be some sort of fault with this PSU. I'll put a tester on it on Monday and see how it looks.
 
Tested it earlier and the voltages are all fine, it just seems to have problems handling a high load.

Ah well, RMA here we come, this is not going to be easy I suspect as it will pass any casual test so I'll need to be very specific on the fault conditions.
 
Teal said:
2 x 150GB Raptor and a single DVD writer.
Click to expand...
Think I read on Tom's about there being a config problem between 8800's and Raptors. Try a different harddisk (non-raptor) if you have one.

Matthew
 
The alternate PC I was using for testing only has a single Samsung Spinpoint and a DVD writer in it and the Antec PSU couldn't power the 8800GTX in that one either.

Also the 700W PSU I swapped in place of the Antec had no problems with the GTX and the Raptors.

Struggling to see any possibility other than the Antec being faulty under load at the moment.
 
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