View Full Version : Could an underpowered system badly impact 6800GT's FPS?

03-27-05, 08:59 PM

I recently upgraded from a 9800pro 128mb to a 6800GT 256mb on a P4 3.06 ghz system and have seen virtually no improvement in any of my games (Doom, FC, HL2 etc), and in some cases my benches have been even worse than the lesser Pro. I have a more detailed account of my situation with the fine folks on B3D over here http://www.beyond3d.com/forum/viewtopic.php?t=21467

But Ill cut to the chase. I think it may be my power supply thats the problem but Im not sure if its the root cause of all this. I found out the amperage on my 350w PSU is 14A on the 12v rail. Now my question is have any of you guys had experience or have heard of a video card (particularly the 6800 series) simply drastically underperforming when underpowered, but not showing any stability issues otherwise? The main reason I didnt suspect the PSU at first was the system was running completely smoothly despite the incredibly low framerates.

03-27-05, 09:06 PM
The people at Beyond3D gave you sound advice and you aren't going to hear anything new here.

1) Your CPU and memory, while something of a limiting factor, are not the main cause of your problem.
2) Your PSU is inadequate.
3) You should have done a clean install of Windows (information you left out of your post here).

Edit: 1024x768 won't do squat for you with that 6800. If that's all you run at, you should have kept your 9800 or gone with the less expensive GeForce 6600 GT.

03-27-05, 09:06 PM
If your running on lower power it actually downclocks the card. Either way you should see some increases in FPS in those games (well, mainly when using AA/AF)

Oh and yes you should do a clean install (thats probably the main problem)

03-27-05, 09:23 PM
Well first of all, your CPU and RAM aren't your problem. A 3.06 is not underpowered and is adequate enough to power a 6800GT, and so is your RAM.

The problem in your case might be that you need to do a complete windows install from the beggining.

Even though you're only running 1024x768, you should still see massive improvement. For example, I run an Athlon XP myself, along with a 6800 GT too. The highest resolution I play games at is 1152x864, and if the game doesn't have that resolution, then I play at 1024x768. Now for a comparison, on another friend's 9800 Pro, he can run FarCry at 1024x768 with all details on and noaa/noaf with good fps average (40-50). On the other hand, if he enables 4xAA/16xAF it's not playable at all, and same deal with Doom3. However, on my computer, I can put on 1152x864 4xAA 16xAF and get like 60fps in both of those games, and even bit better with 1024x768.

So what you should be doing is run 4xAA/16xAF for every game you have, but the performance you should be getting is still like twice that of a 9800 Pro, because you sure as hell won't get better than 25-30fps average on a 9800 Pro in FarCry at 1024x768 4xAA 16xAF, with a 6800GT however, you'll get 60-70fps.

03-27-05, 11:41 PM
The people at Beyond3D gave you sound advice and you aren't going to hear anything new here.

Actually, hearing I should do a clean windows install is something new. :) Folks at B3D and Guru3D said it wasn't at all necessary, so I guess there's some conflicting views on the value of that. May I ask whats the logic of a clean install for a new video card, even if you make sure all the previous drivers are wiped out properly? Im not saying its wrong but Im curious how not having a fresh install could possibly impact a card with this type of horsepower this severly.

Which led me to the PSU situation. In the B3D thread someone mentioned reading a couple accounts on nvnews that an underpowered PSU hampered the 6800 series' FPS performance. I checked Riva Tuner's hardware monitoring while I ran several games and it reported no "self-underclock" of any kind. So Im not sure where this leaves me at this point. I do appreciate any feedback though, Im rather stuck here.

03-27-05, 11:47 PM
There is no reason to have to uninstall/reinstall windows when switching vendors. All you need to do is run driver cleaner and install your new hardware/drivers. Heck I dont even do that. I just use the regular uninstall process when switching vendors and it works fine.

03-28-05, 05:45 AM
There is no reason to have to uninstall/reinstall windows when switching vendors.

Yes there is. The video card is not performing as it should. Doing a clean install is a way to eliminate one possible cause of the problem.

03-28-05, 06:36 AM
Yes there is. The video card is not performing as it should. Doing a clean install is a way to eliminate one possible cause of the problem.

You mean all possible software problems. 95% of the time. An Uninstall/reinstall can be avoided. Its like taking a sledge hammer to swat a fly. Its pure overkill IMO. I very much doubt the problems being noted here warrant a reinstall.

03-28-05, 07:00 AM
A reinstall costs you nothing except time. If that doesn't work, then the likely culprit is the power supply. It's best to try and take the approaches that don't cost you any money first IMO.

03-28-05, 08:44 AM
Oh well. We'll agree to disagree here. I think reinstalls should be the absolute last thing you do when troubleshooting. Last resort type thing. I really dont think a reinstall is going to fix his problems though.

03-28-05, 08:53 AM
I found when moving from the 9700 Pro a few nigglies crept up, even when uninstalling drivers in safe mode and then using driver cleaner. Same happened when I did the ti4200 to 9700 Pro. So IMPO fresh install is a must when moving to differnt IHV cards.

03-28-05, 09:16 AM
I would recommend a reinstall of the operating system as a last resort option only.

If you have done all the hardware troubleshooting that is.

From what you have posted, it seems like it's more of a hardware issue (power supply), than an operating system.


Sick Willie
03-30-05, 09:00 AM
I tend to agree with ChrisRay that a clean install of Windows because of a change in video card vendors is overkill in the majority of situations. As a troubleshooting tool, however, I would probably do a clean install on a spare hard drive - just to see what happens. I don't think it will fix the problem and this way, he still has his Windows installation intact.

I have one machine at work that has been from an MSI K7N420-Pro (nf1)->Asus A7V8X-MX->Asus K8N-E Deluxe (nf3)->Chaintech VNF4-Ultra (nf4), with video cards: onboard GF2->ATI 9800 Pro->Asus EN6600GT (PCIe)->ATI X800XL (PCIe). All on the same (or repair install) copy of XP Pro. Other than the mentioned repair install (only when going from nf1 to VIA), I have merely un-installed the old drivers and installed the new ones. This machine runs benchmarks at the expected level and plays games without issue. OTOH, I have a machine at home that would not go from an A7N8X-Deluxe (nf2) to K8N-E Deluxe (nf3) without a clean install. Even a repair install wouldn't work. Go figure.

03-30-05, 10:18 AM
I'm going to agree with ChrisRay as well - a reinstall is definitely overkill in a situation like this and should be the last thing you try.

Saturn was right though, your CPU and RAM are not a limiting factor in this case and your PSU is inadequate. Another detail we have not been provided is whether or not you are using anisotropic filtering or full-screen antialiasing. If you are not, you won't notice any difference at 1024x768. My old GeForce 4 Ti4600 ran UT2K4 just as well as my 6800GT at 1024x768 0xAA 0xAF. Once I turned the resolution to 1280x1024, and 4xAA 4xAF, my performance remained excellent on the 6800GT while it was unplayable on the 4600. You would notice the same thing. If you've got a 6800GT 1280x1024 is the minimum resolution you should be running, and high image quality settings should be a priority. It's what you paid for, after all.

FWIW my 3DMark05 score was in the 2000-range. It's a useless benchmark entirely dependant upon driver tweaks and is not representative of gameplay.

As some posters on the b3d forums said, we need more information from you to give you sound advice.

03-30-05, 10:53 AM
Your 6800GT doesn't use the 12v rail, unless it's using it from the molex connectors?

What are the specs with the rest of your system? You can go here to get an idea of how much power your system needs. http://www.3dcool.com/PWC.asp.
That power estimation is on the high end but it will give you an idea of the power requirements of your system. What brand of 6800GT do you own? Some 6800's have only 1 molex connector that is required.

If you have 2 hard drives with that 6800, a DVD/CD writer/reader and your memory motherboard combo, then your 350w while low would not be the problem. This doesn't take into account unstable voltages. The 6800 GT requires more power then your 9800 did. Get something to monitor your voltages from your power supply. Mother board monitor is a good choice and is pretty accurate. Also you can stick the leads from a multimeter into a molex connector and be even more accurate. Keep in mind you need to monitor those voltages at idle and during loads to determine if your voltages are stable. Normally as a general guide, you shouldn't have anymore then a 5% fluctuation from the base voltage is ideal.

If it was me, I would get another PSU (another 100w atleast) and reinstall XP. This will ensure a clean OS with drivers and ensure my power hungry 6800 had enough power to perform at her optimal level :)

03-30-05, 11:33 AM
The 6800GT uses the 12v rail. And what other connectors would he be using but molex connectors? He's running an older P4, this isn't a PCI-E. Almost every single 6800GT requires only one molex connector, with the exception of the Asus "V9999GT". Voltage problems would manifest in the form of system shutdowns, not slow 3D performance. His 350W supply has a low-rated 14A on the 12V rail and this is most likely a cause for concern. Re-installing Windows is, as I said before, a last resort and most likely will not do anything you couldn't do by troubleshooting.

If you want my opinion, this power supply should be the one you get:


It's a bit pricey but you get what you pay for, and in my opinion a high-quality PSU is essential in any computer. The OCZ Powerstream series are some of the best PSUs you can buy (I believe they are repackaged Tagans, correct me if I'm wrong).

03-30-05, 04:39 PM
I was referring to the 3.3v AGP slot voltage or in other words, he isn't using 12v from the AGP slot hence if it's using the 12v rail, it has to come from the molex connectors. If he only has one hard drive and say a cdrom/dvd rom then that 350w PSU can handle his 6800GT. I do agree that his PSU is a concern, it just depends on his system comfiguration and how stable his voltages are.

03-30-05, 05:20 PM
Why doesn't he just try the FREE way instead of forking out cash instead? It doesn't cost him ANY money to re-install Windows with everything. It costs money to buy a new power supply. What if a simple Windows install will solve everything? Now wouldn't that be better than forking out $70 for a new PSU. :rolleyes: