Possible PSU problem after adding a 2900XT.

[Matt2]

After adding my 2900XT, I've been experiencing strange instability issues.

System Specs:
Opty 170 @ 2.6GHZ
DFI CFX3200 mobo
2GB OCZ GamerXtreme OC4000
2900XT
Silverstone ST56F 560w, 36a on dual rail
SB Audigy2
Seagate Barracuda 120GB 7200.8
NEC 3550 DVD Burner
Linksys PCI Wireless adapter
Koolance Exos WC System

Ok, my CPU used to hit 2.8GHZ stable at about 1.5v. At first when I installed the card, I could not get passed 2.6GHZ w/1.4v. Anything higher than that whether it was voltage or mhz and my PC would completely shutdown during a 3DMark06 run. If I was at 2.6GHZ, everything ran perfectly fine.

I played around for a while and swapped the positions of the PCI-E connectors. The result was 2.7GHZ stable and I can even overclock the 2900XT to 825/910 with no problems. Trying for 2.8GHZ resulted in blue screens now instead of shutdowns. The error message in the BlueScreens is the infamous, "IRQL_NOT_LESS_OR_EQUAL".

Could my system be drawing close to 560w? I thought this PSU would be more than enough, but now I am afraid of pushing it to the point where it explodes and takes my system with it.

Anyone else running a similar setup? What PSU would you guys recommend for $150 or less?

 

[John]

IIRC the 2900XT pulls roughly 14A under load, and your entire rig will probably pull 300W from the psu under a full load. Do you have both 6-pin pci-e connectors hooked up?

 

[Matt2]

Originally posted by: John
IIRC the 2900XT pulls roughly 14A under load, and your entire rig will probably pull 300W from the psu under a full load. Do you have both 6-pin pci-e connectors hooked up?

Yes, I have both 6-pins connected. When I swapped the connectors, so that the one that wasnin the 6-pin was in the 8-pin and the 8-pin in the 6-pin, I gained more stability.

Not sure what's going on here. If my system really does only pull 300w, I should have more than enough headroom to run this card without breaking too much of a sweat.

 

[SparkyJJO]

Remember some of that 560W is in the 3.3V and 5V rails. Not all of it is 12V. Most you can pull from the 12V is 432W.

Sounds like at first you were just overloading one of the rails. Now it sounds like your OC just isn't quite fully stable. Happened to me once, 2.8 was stable, then when I re-OC'd later after playing around I was no longer able to hit 2.8 stable it seemed (was getting BSODs like that). Some setting someplace wasn't quite right, never did figure it out so I stayed at 2.7GHz. I am just now trying to get back up there again (and a bit beyond, reaching for 3GHz but it isn't coming easily).

 

[John]

Originally posted by: SparkyJJO
Remember some of that 560W is in the 3.3V and 5V rails. Not all of it is 12V. Most you can pull from the 12V is 432W.

AFAIK both PCIe connectors share the same 12V rail, and each rail is limited to 18A and peaks @ 19A (228W), so I have no idea why swapping them would affect the stability. Hopefully someone else chimes in with a detailed response.

 

[SparkyJJO]

Originally posted by: John

Originally posted by: SparkyJJO
Remember some of that 560W is in the 3.3V and 5V rails. Not all of it is 12V. Most you can pull from the 12V is 432W.

AFAIK both PCIe connectors share the same 12V rail, and each rail is limited to 18A and peaks @ 19A (228W), so I have no idea why swapping them would affect the stability. Hopefully someone else chimes in with a detailed response.

Depends on the PSU. Some have the CPU and PCIe 1 on one rail, peripherals and PCIe 2 on the second. Some have it a different way. My guess his PSU has it with one PCIe on one rail and the other PCIe on the other.

 

[John]

I am fully aware that not all multi-rail psu's offer independent current limited rails. Regardless of the rail distribution on the ST56F, I cannot comprehend how swapping the PCIe connectors from one port to another on the 2900XT affect the overall stability of the system.

 

[jedisoulfly]

if u only use 2 6pin connectors you might not be getting enough power. for overclocking ati says you need the 6pin and the 8pin. I dont know maybe your not getting full power to the card?

http://ati.amd.com/products/Ra...2900/requirements.html