Comments on: Why Isn’t SLI/CrossFire A No-Brainer?

By: Ernest Christley

Ernest Christley — Mon, 14 Mar 2011 19:08:18 +0000

SLI does have the advantage that it allows you to run more than two monitors. I have three 22″ monitors that I built a mount for so that they wrap around. for a 145 degree view.
I just upgraded the cards from 8600GTs to 9800GTs, which is about the most wattage my computer is able to handle (9800GTs can be had for $60 each right now). I’m here because the ground textures are not drawn by the second video card for some reason. The ground is just black, with objects and roads sitting on top.

By: Chris

Chris — Wed, 13 Jan 2010 21:53:33 +0000

Hey Ben,

I just ran several test runs on one of my rigs with SLI. After reading some of your posts, it got me wondering if it was even worth the extra wattage, so... The system is a dual-boot with XP SP3 and Vista Ultimate 32-bit, 4GB SLI-ready RAM, and twin GeForce 9800 GTX+ in SLI config. CPU is a Core 2 Duo, OC to 2.98GHz.

What I found: no matter what settings used, SLI made no difference in either OS. In fact, I squeezed about 4 FPS more with SLI disabled as I flew over a small city with objects at "megatons." Framerate was only about 5 more in XP than Vista. Being a dual-boot system, all hardware is precisely the same, though drivers of course may be slightly different, but this is still a good test.

Overall, I now totally agree with you that SLI is pretty much a waste of money in this context.

-Chris

By: alaskanCrab

alaskanCrab — Mon, 21 Dec 2009 12:47:39 +0000

I think the biggest problem is the fact that most of the PC games today are simply just ports limited by the console hardware restrictions. I could put two Nvidia 295 in a machine but what is that going to get me when the object and texture assets are limited to something less than an 8000 series at best. SLi might be a great idea on paper but with Nvidia these days you really have to question their motives. Are they doing this for gamers or the High Performance Computing market?

As I mentioned I'd rather see improvements elsewhere that'll help destroy that FSX beast for good. :) And when I do upgrade to the Fermi chances are I'll only be getting one card, and will focus on the fastest core and plenty of VRAM.

By: Benjamin Supnik

Benjamin Supnik — Mon, 21 Dec 2009 10:43:10 +0000

"That's your problem now isn't it."

Lucky me. :-)

Seriously, I do not know if SLI is even architecturally useful for X-Plane...our use of render-to-texture causes serious issues, ones that may not be addressable using current APIs.

I also question how cost effective SLI is - it would be a way for me to spend finite optimization time only improving the framerate for the subset of users who have AT LEAST one good graphics card already.

By: alaskanCrab

alaskanCrab — Mon, 21 Dec 2009 02:00:06 +0000

Hi Ben,

Well remember a few months ago when you said X-plane shouldn't work in SLi mode because of the way the texturing works. You were spot on. I was having issues maintaining the minimum 19FPS and was getting those dang warnings. Disabled SLi in the Nvidia control panel and I was screaming at 70FPS. :)

So as it stands the current engine cannot be run in SLi mode at all. Now my understanding was that Nvidia goes around tweaking apps to get SLi support out of older products like FSX. Well it does achieve this and it's about less than 10% improvement, which leads me to think the only improvement here is the final rasterization.

As far as X-plane working with SLi in the future, well that's your problem now isn't it. But If I were you, I'd explore other avenues first.