View Full Version : PSU and video card performance

07-29-03, 06:40 PM
I experimented with multiple power supplies on a SFF (shoebox computer) and a NVIDIA graphics card with external power connector (FX 5800 Ultra). The stock PSU for a SFF is a paltry 200 W, which is not sufficient for all the gear I had in the machine PLUS the NVIDIA card. The machine would bluescreen whenever I launched a 3D game or benchmark. This lead me to connect the video card to an external PSU. Anyone with a graphics card that has a PSU molex connector may be interested in my findings.

In order for the external ATX PSU to power on, I hooked it to an empty ATX motherboard (no CPU or RAM) and a power switch. That board no longer works properly. I don't know if there's any relationship between the board failure and operating it for a few days without any CPU or memories, but you may wish to hook up a switch to the ATX PSU connector instead of using a board.

On an external PSU, the graphics card received enough juice for 3D modes. As far as metrics go, the system scored higher Onionmarks by increasing the PSU wattage from 190->200->250->300->350 Watts. IIRC the Onionmarks 01 were
- 13.5K with 190 W.
- 14.2K with 200 W.
- 15.7K with 250 W.
- 16.9K with 300 W.
- 17.0K with 350 W.

Onionmarks 03
- 5333 with 200 W http://service.futuremark.com/compare?2k3=962645
- 6221 with 350 W http://service.futuremark.com/compare?2k3=848363

I don't own anything larger than an Antec 350 W, but the increasing scores lead me to believe the card's performance would go slightly higher with a 400-500 W PSU.

The Baron
07-29-03, 08:58 PM
Interesting. I think though that what you saw might be attributed to the card being provided stable, regular voltages by the Antec PSU (not like mine did. HAH!) rather than having it fluctuate from the strain of all of the devices in the 200W PSU.

Now, if they were all PSUs from reputable brands, that'd be another story. But, I haven't seen an Antec or Enermax 190W or 200W ever, so I don't know about those.

An interesting find, though. Just goes to show that skimping on the PSU means that you should probably feel very stupid.

07-29-03, 09:42 PM
Hey ricercar,

you might wanna give Speed Fan (http://www.almico.com/speedfan.php) a try and see what's going on with your +12 volt DC rails. Anything higher than +12.60 is pretty bad, meaning your system components are starving for power. If it is under +12.00... your components aren't even affecting the power supply... that is good. :D

It will say which mobo(s) it is compatible with, check it out.



07-30-03, 08:41 AM

I'd just like to say that if you're REALLY stupid like me, the first time you install a GeForce FX, you don't realize that you need external power, hehe. Fixed now :)

Another thing: The GFFX 5800U takes 106W of power! It's a real *monster*. I can't even understand how it ran with a 200W PSU...


07-30-03, 10:50 AM
Originally posted by Uttar

I'd just like to say that if you're REALLY stupid like me, the first time you install a GeForce FX, you don't realize that you need external power, hehe. Fixed now :)

Another thing: The GFFX 5800U takes 106W of power! It's a real *monster*. I can't even understand how it ran with a 200W PSU...


If I'm reading the original post correctly, the graphics card basically had the PSU to itself, which is how it worked with a 200W PSU I assume.


07-30-03, 04:26 PM
The 5800 U can share a 200 W Shuttle PSU with a Barton 3000+ SFF system indefinitely in 2D modes. I run the 5800 U that way these days for email, websurfing, DVD watching, MP3 listening, and even forrays into UT2003 at 800x600.

The 200 W PSU cannot be shared and run the 5800 U 3D pipeline at a larger resolutions. If the shared-PSU tries to run the 3D pipeline at 1024x768, machine bluescreens with a nv~~~.dll error.

With a separate/dedicated 190 W or 200 W PSU, the 5800 U runs 3D at 1024x768, but the benchmarks aren't as good as with a more powerful 250+ W PSU. My LCDs max resolution is 10x7, so I haven't performed any larger <resolution vs PSU> tests. Hmm. Now I want to borrow monitor and see if the 350 W PSU can run the 3D pipeline at 1600 ...

BTW, that weird 190 W PSU came from an old www.Magma.com 2-slot PCI expansion chassis I bought from eBay for an experiment on my PowerBook...

07-30-03, 05:05 PM
Hmmm that explained why I have low score around 10,800 on 3DMark 2001SE on my Leadtek 5900 Ultra running on Suntek 300 Watt power supply. I wonder how much power 5900 Ultra use and is Antec brand power supplies the best one?

I am surprised my Leadtek 5900 Ultra ran fine at the high resolution 1600x1200 and 1920x1440 on Unreal 2. I guess benchmarks will need large power supply.

The Baron
07-30-03, 07:30 PM
Antec/Enermax/Zalman/Vantec. Not necessarily in that order.

I don't think I'd buy another Antec PSU. But hey, that's just me, and it might be fine.

But I'm the only person I know that has had a problem with an Antec PSU. But, speaking of that PSU, I need to go stab FedEx in the eye for lying about trying to deliver my package (it was on the truck a day early, and they said they attempted delivery--but, naturally, I ensured somebody was home at all times. they just didn't come.).

07-30-03, 11:48 PM
This needs further testing with better PSUs...

I wonder if the same applies to the Radeon 9700/9800 since both do have the power connector (as well as the ancient Voodoo 5 which first suggested the need for it)

08-08-03, 12:09 AM
I have a Sparkle 350w PSU, I have read reviews that this PSU is one of the best 350's and outputs above what it's rated for..

my readings are
12+ +11.865
12- -12.281
5+ +5.056
5- -5.099

do these seem ok?? im using a Albatron 5900pv

on my system 3dmark2k1 gets me 15k @ stock speed
I had a 9500np -> 9700 that got me 18k @ 400/310

3dmark03 5400 @ stock
3dmark03 6019 @ OC (can't remember what it was I auto detected it)

9500np -> 9700 3dmark03 5829

08-08-03, 01:58 AM
I imagine it is ok although you want the rails to sit as close to there designated states as much as possible. Some fluctuate really bad while others stay rock steady with a .1 change under load.

Doesn't appear that your components are starving and I have read the reviews on sparkel as well. I got one for a backup pc and it performs quite well. :)