What do we know about SLI working with FSX

[Flight Ace]

What do we know about SLI working with FSX?


There have been many comments made about SLI and SFX. I have researched this subject and based on my understanding of a number of posts and pertinent articles, have summarized in simple statements my findings. Please note that I am a novice with this new technology so if there are any concerns feel free to shoot me down.

What is SLI?

NVidia SLI means Scalable Link Interface. It uses an operational mode called Split Frame Rendering (SFR)

How does it work?

A frame is split in half and the two video cards render their own part of the frame. Simply stated, SLI is using two video cards, with a compatible SLI driver, to process instructions received from SFX software through the CPU to send complex video scenes to one display. Stated another way, to get a measured increase in performance, you employ two video cards instead of one using an SLI motherboard without changing CPU attributes.

How does SLI relate to FSX?

SLI works with FSX and most other software. Given two high-end video cards and CPU: and appropriate RAM, you would expect an improvement with performance. However in those cases where one employs reasonably high-end video cards and only a mediocre CPU, a loss in performance is likely. This is not the fault of SLI but most probably would be caused by a bottleneck of instructions at the CPU.

All those people recommending the use of SLI in a new rig I believe are correct. An SLI configuration including 64bit Vista and DX10 several years from now running FS11 should be a good fit.

[NickN]

SLi is all about the drivers and your support hardware, not FSX

SLi works fine in FSX as long as the drivers are working and you have the right monitor for it. It is my understanding Vista and SLi do not play well together.

If you are not running a monitor(s) with very high resolution (2xx X 1xxx and above) SLi is not worth the investment for FSX


The advantage SLi provides is only in very high resolutions and 8-16x AA

otherwise you will not see any advantage

[Ashton Lawson]

Just to add to Nick's comments, Vista SLI support and stuff is on-par with XP.  Sure, the performance may not be as great, but the actual percentage increase with SLI is roughly the same.

and Nick, you forgot an x, in the 2xx bit.  2560x1600 is teh best.  Toshiba, or somone like that are making a 3xxx x 2xxx something monitor thats 22", what a waste...

And Split Frame Rendering is not the only way, there is also alternate frame rendering, where the graphics cards take turns rendering a scene.  There is also some other hybrid mode, but i forgot the name.  THere's a lot of documentation on SLI on www.nhancer.com.

I think SFR is the best method to use, but first, use a benchmarking type thing to see how evenly the rendering is split between the cards.  If one card gets the majority of the screen, and the other card very little, then its best to switch to AFR...

[garymbuska]

My son has a system with two 8800 GTS video cards and is using Vista (32 bitmode) and to my knowledge he has had no problems with it. Granted he does not have any version of FS installed but does play several other games that are equally graphic intensive. HALO3  8-)

[memorgan]

Having read the posts in this thread, I'm getting a little worried now.  Just bought a replacement for my 4 year old P4 3ghz,  Can anyone please confirm that what I bought will be OK for FSXm its about as much as I can afford:

Intel

[Dwhiskie]

Im only running a core 2 duo and it runs fine at around 25fps in most areas  so your setup will run in very good  but dont expect to max out "all" the sliders

[Ashton Lawson]

[quote]Having read the posts in this thread, I'm getting a little worried now.

[Flight Ace]

SLi is all about the drivers and your support hardware, not FSX

SLi works fine in FSX as long as the drivers are working and you have the right monitor for it. It is my understanding Vista and SLi do not play well together.

If you are not running a monitor(s) with very high resolution (2xx X 1xxx and above) SLi is not worth the investment for FSX


The advantage SLi provides is only in very high resolutions and 8-16x AA

otherwise you will not see any advantage

Nick, there is no quarrel about SLI being about drivers. In fact proper functioning of all video cards is about the drivers. In reference to support hardware I am curious if an SLI configuration would provide a benefit when driving a 22

[memorgan]

Thanks for the advice, unfortunately, the spec I have was all I can afford.  I was advised that the 8600s in SLI were preferable to a single 8800 card, which is why I went with it.  I specifically told them that I primarily wanted to use this for FSX.  Still, better than my old rig!    As to resolutions, this is entirely new ground for me, always had single monitor system, so I was going to ask the community for suggestions about how to set-up a 3 monitor sysytem and also try to find out the best resolution for them.
I have to say I was really looking forward to getting the system, but I looks like I'm gonna be disappointed before I even start!

[Flight Ace]

[quote]Thanks for the advice, unfortunately, the spec I have was all I can afford.

[NickN]

2560x1600 or higher with 8-32x AA

if you are not running that in FSX, SLi is worthless and you must also have the fastest processor available to do it as well because of the massive CPU calls the title forces. In FSX those are the facts due to how the title is written, in other games its different.


If you are buying SLi for FSX, dont bother until after the next generation of VC and processors. Even so the cards can do it, the CPU is wacked to death running that resolution



If you cant do 2560x1600 or higher with 8-32x AA, dont bother and if your monitor can do that, expect lags in frames with FSX

[Flight Ace]

2560x1600 or higher with 8-32x AA

if you are not running that in FSX, SLi is worthless and you must also have the fastest processor available to do it as well because of the massive CPU calls the title forces. In FSX those are the facts due to how the title is written, in other games its different.


If you are buying SLi for FSX, dont bother until after the next generation of VC and processors. Even so the cards can do it, the CPU is wacked to death running that resolution



If you cant do 2560x1600 or higher with 8-32x AA, dont bother and if your monitor can do that, expect lags in frames with FSX

Nick,

Thanks for the info

[NickN]

2560x1600 or higher with 8-32x AA

if you are not running that in FSX, SLi is worthless and you must also have the fastest processor available to do it as well because of the massive CPU calls the title forces. In FSX those are the facts due to how the title is written, in other games its different.


If you are buying SLi for FSX, dont bother until after the next generation of VC and processors. Even so the cards can do it, the CPU is wacked to death running that resolution



If you cant do 2560x1600 or higher with 8-32x AA, dont bother and if your monitor can do that, expect lags in frames with FSX

Nick,

Thanks for the info

no problem

the next round of dual-GPU video cards and quad cores will run SLi much better but their cost will be high for at least 6 months.

I suspect SLI in FSX will become worth the investment but not for another year, and even then you must be running the right monitor(s) to take advantage of it.

[memorgan]

Hi, thanks for the advice in earlier post.  I took this onboard, and decided to look further into this, I could get twin 8800GT cards.  I have also been told that a better bet would be to go for the ATI 2900XT card with a secondary card for the 3rd monitor, now I'm just plain confused. (the machine with this card also comes with 8Gb ram and 1.5Tb striped raid storage).  I cancelled the order for my new rig til I can get my head round it all!!!
Any further comments gratefully received.

[NickN]

1. The 8600 video card is a joke for a high end system. You are better off on a single 512MB 7900-7950GTX. The only thing the 8600 will do for you is give you low end DX10 support. Instead of buying 2 8600 cards I would go with a single 8800GTX or wait a bit longer for the next generation fo cards to hit the streets, which is so close right now I would not bother purchasing till then. Wait and see how the new ATi cards hold up because they will NOT be like the HD2900XT. In fact they will run much cooler and much faster. The dual GPU video cards will also be hitting the streets.

2. 8 gigs of memory is overkill. 4 would be fine and I can even go with the 8 if the rig is going to be used for things like video editing, but, if you are not going to be running a 64bit operating system (WindowsXP x64 or Vista x64) 8 gigs is a total waste because the 32 bit versions of the OS will never use more than 3.2.

3. I have tested FSX installs on many, many different controllers and drives. In all of the RAID tests, any STRIPE below 128K (on a 2 drive RAID