Tweaking around a CPU bottleneck

As noted in another of my posts today, my doom3 FPS is virtually unaffected by quality and resolution settings (and it ain't great). In short, my card is capable of rendering more than my system can throw at it.

So how can I eek out some more performance?

Game and driver tweaks:

I have not yet played with "decals," "specular lighting," etc, but I'm wondering if someone here can tell me if those settings (or any others) can be tweaked to ease the CPU load. I have Rivatuner, and am comfortable making tweaks, so long as someone isn't too vague about what they mean (I'm new to Rivatuner, not OC).

Pushing the system (OC):

Based on the former assumption, it will do no good to OC the video. I managed a partial soft-mod to 6800GT (12x1,6vp). Again, no change in Doom FPS, but at least I know it's available, and I gained 108 points in 3DMark03. That leaves the CPU/FSB. I have a !#$)*& palomino core which I wouldn't lament frying. My current thoughts are to crank up the voltage and step the FSB up until it bleeds. However, I know the palomino doesn't respond very well to that, and I cannot control VDIMM with my mobo. I have "overkill" memory (Crucial PC3200 XMS) purchased to go with my next system. It's running substantially below its rated frequency, and I do not know what memory timings might be attainable at this speed, or if even if RAM timings are affected by FSB.

I have great "air" cooling on the CPU, and it's not worth much. The RAM is sacred, and I don't want to hurt it. AGP is running at 4x (w/o fast writes), and the specific card is a LeadTek A400 TDH (6800nu).

So, what's worth trying, and what's a waste of time? Note that at 37 FPS, a few more is a decent gain.

Well it looks like I've come to the end of this road. I have attained 47 FPS in Doom 3 timedemo, and 7769 3DM03.

I managed to get back to my 10% overclock (FSB 147; 1691Mhz from 1533) with perfect stability. This was attained with adjusted VCore of +0.075v. The next jump of +0.100v was not enough to gain stability at FSB 150. I didn't fiddle around with the 1-2 Mhz I might have gained. I might have attained stability at 150 FSB if I'd cranked this howeling fan back up to 12v, but it's already noisy enough to dampen the "mood" of Doom.

I gained a little extra in 3DM03 when I unlocked the 6th pixel shader. One of the 4 extra pipelines is buggy. I'm not sure if there is any way to make it behave through additional tweaks, drivers, or voltage.

Basically, when your machine is as CPU strapped as mine, you can crank up all the eye candy in Doom3, except Shadows. That was the one thing that made a significant difference in FPS. I gained 9 more frames (23%) to finally top out at 48 on timedemo. From 1280x1024, with "high" quality and all the goodies turned on (except shadows), I gained only 2FPS at 640x480 "low" quality, with all the goodies turned off. Note that "high quality" turns on a handful of features behind the scenes such as anisotropic filtering. Also, the shadows setting will not remain off (version 1.1). You must script it off, or put up with turning it off each time you restart the game.

Now, timedemo isn't the end-all be-all of playability metrics. There are a variety of doom engine tweaks, particularly those concerning texture caching, that many other people have gone into great detail on. I won't copy all that here.

Does your mobo support 200fsb? If it does unlock that chip and lower the multi and raise the fsb up to 200fsb or as high as you can stable.

omaticrail said:

So, what's worth trying, and what's a waste of time? Note that at 37 FPS, a few more is a decent gain.

Click to expand...

What would be worth trying, is getting a better CPU. That seems that would be the easy part, considering you can afford a 6800?

football said:

What would be worth trying, is getting a better CPU. That seems that would be the easy part, considering you can afford a 6800?

Click to expand...

Good point, but there are complications. I'm torn between CPU/mobo options. My mobo doesn't support significantly better processors. Barton cores and 200 FSB are right out. The 6800 gained me far more than I'd have achieved through a CPU upgrade with my old GF3, and I know AGP (though on its way out) is still more stable than any of today's CPU sockets.

If the AMD socket battle (and prices) settle down reasonably soon, I'll go for the winner. Otherwise, I'll just go with the combination of mobile Barton and NF7s. Typical though....the price on that combination at newegg was $30 cheaper 2 weeks ago. Back to $200.

Yeah, but.....

A 2500 barton is way better than a 1600+XP, and that wouldn't be all that much, especially since you could sell the 1600+ and be out of $30 total for the cpu.

check the classifieds: click not too bad a deal...