3+ Monitor Setup -- PCIe x16 vs x8

My first question on this goes out to Wendell. 

Wendell, what do you use for your crazy 5 or 6 monitor setups? Do you run 2 nVidia or AMD cards in your systems or some other alternative? 

What I want to do is have 4 monitor setup. I have here my HD monitor (via hdmi) I use for games and other main productivity stuff and 3 regular VGA flat-panels. I have one of the VGA monitors connected for now and I'd like to have this setup just so that I have more space to throw windows onto. I have the Asus Sabertooth p67 motherboard and PNY's GTX 560ti GPU. I'd like to get at least 3 monitors going from this.

My second question is regarding to bus speed on PCIe. I have my 560ti running on the x16 link. I also have a second PCIe on this motherboard but it runs at x8 and enabling that cuts the first PCIe bus down to x8 also. So I either choose two GPUs at x8 or one at x16. What difference in games would that do going from a x16 link to x8? I ask because if two GPUs is the only answer to what my first question is about then I'll just throw in this old GT 8500 I bought a long time ago. 

The 8500 also brings me to another question. I've never played around with 2+ GPUs in one system before, so I also ask: what would miss-matching these GPUs do to my performance in games? Both the 560ti and 8500 have the SLI finger to be linked. EDIT: SLI no longer relevant to my question.

Also if I did include the 8500, how would the system as a whole handle graphics? Minecraft for example, if it was on my main HD display I assume the 560ti would render for it and if I moved the Minecraft window to another display running off of the 8500 then I assume the render job would transfer... or does it? 


1. I am interested in responses to this question as well myself :)

2. Going from x16 to x8 won't make much of a difference. Especially with a 560ti. Plenty of bandwidth at x8. Now I have seen that a x4 slot does show a difference in performance.

3. You would not use the SLI bridge for what you are trying to do. You will want to run 2 independant GPUs. Besides, the GPUs have to be the same for SLI to work.

I couldn't even get the SLI bridge to reach anyway, lol. I actually went ahead and put in the 8500. I have two displays running from that and my HD display running off the 560ti. You're right about the bandwidth. I saw no impact what-so-ever in various games I tested running in x8. This is nice because now I can actually take advantage of nVidia's power saving technology on the 560ti now that its running just one display.

Something odd about the 8500 though. I noticed through EVGA Precision X that its running at 1.2v. To me that seems a bit high compared to the 1.0v my 560ti runs at when left at stock settings. As a result the 8500 hangs around 62°C with 0% load ambient temps at about 24°C. I guess it just normally runs this warm?

So, after playing around with this 560ti + 8500 setup I've discovered that running x8 vs x16 does make a difference. If your graphics card doesn't have enough vram it will swap with system ram. If your gpu is swapping memory, then it will need bus speed to do that. Testing Minecraft with a 128x128 resolution texture pack, I discovered that my 560ti with 1GB vram was using 1012mb of memory and 78% - 99% bus load with the 8500 installed at a x8 link and less than 20fps. With the 560ti by itself at a x16 link, the bus load was at most 50% and doing about 80 - 120 fps. That is a shame in my case, I'm going to miss my third monitor until I upgrade to a 700 series card.

Ahh, I didn't think about the impact when the VRAM was full. That makes perfect sense that it would be very hurtful at the point where it has to swap data across the bus a lot. Thanks for the update!