Multiboxing Wiki - Multicpu, Multigpu, Multiharddrive, Multimonitor, etc and Bounded Issues. Revision 3. Work in Progress.

[vchi]

6. GPU Bound:
My monitor and GPU setup is as follows:
Monitor A, B, C, D (each running at 2560x1600)
GPU 0 and GPU 1 (non-SLI)
Monitors arrange from left to right on the same level of vision.
A B C D
GPU 0 drives monitor A and B.
GPU 1 drives monitor C and D.
WoW1 and WoW5 appears on monitor B.
WoW2 appears on monitor C.
WoW3 and WoW4 appears on monitor D.
WoW grid coordinates and sizes:
Instance - X Coordinates - Y Coordinates - Resolution
WoW1 - 2560 - 0 - 1920x1200
WoW2 - 7680 - 0 - 1920x1200
WoW3 - 8320 - 400 - 1920x1200
WoW4 - 5120 - 0 - 1920x1200
WoW5 - 3200 - 400 - 1920x1200


Note 1: In a MS windows environment, the screen coordinates are defined as primary monitor with the top left hand corner of the screen defined as coordinates 0,0 with the numbers increasing in a down and right fashion. If you switch the primary monitor to a different monitor, then the new primary monitor with the top left hand corner of the screen would be defined as coordinates 0,0 with monitor(s) to the left and above of the primary monitor being in the negative coordinate space.
Note 2: In Vista, you cannot mix and match different GPU vendors (not the card vendors but the GPU processor manufacturers, i.e. AMD ATI, Nvidia, Intel, S3 or etc). By design Vista will prevent you or it will revert to generic drivers to ensure system stability. In the previous operating systems, you could mix and match different vendors, however based on MS long-term bug-report and crash analysis, they determined a majority of the stability issues were related to the GPU drivers (I do not have the link to it, I will try to google it for the next revision). In terms of mix and matching different GPU families (i.e. Nvidia GTX 200 series with Nvidia GeForce 8000 series), you can but it is very dependent on whether or not the latest drivers support both families at the same time. Vista limits you to one set of drivers for all video cards. If your video drivers are unified and supports the video cards currently in your machine, then you are good.
Note 3: My current 8 core setup does not have a mix and match different GPU family, so I can't tell you with concrete facts if it would work or how fast it would be. Depending on available time, I have an old Nvidia GeForce 8800 GTX that is floating as a spare part that I could use with my current setup and substitute one of the Nvidia GTX 280 series with it and test this out.
Note 4: For applications to benefit from CrossFire / SLI, three conditions must be met:
1. Operating System support
2. Driver support
3. Applications specifically written to taken advantage of a CrossFire / SLI
Condition 1 and 2 are already met. However in terms of WoW, condition 3 is not met. WoW is not specifically written to take advantage of a CrossFire / SLI setup. This is probably due to programming cost of building, testing, and maintaining that support if they so choose to add it. Even if they were to add it in a future version of WoW, there will two sets of source codes to maintain and over the long-term would add up in cost and the man-hours. This leads to another issue of coarse vs fine multi-threaded issues which I will cover in the next revision.
Drivers and the driver control panel can to some extent force WoW to enable the CrossFire / SLI support, but that would be stretching it.
Note 5: Spanning displays do not offer performance improvement. Monitor(s) connected to the same GPU (non CrossFire / SLI) still have the same GPU rendering size of workload = number of monitors * each monitor's workload. However, if the drivers provide support for rendering to multiple monitors and multi video card, there is no bus contention or bandwidth issues between the said video cards, and the application is written to take advantage of this setup, then there is a possibility for performance improvement.
Note 6: There's been unconfirmed reports of certain CPU/GPU combination and the Nvidia GTX 200's graphic cards not reaching it's maximum performance due to the Nvidia graphic drivers not being optimized for a 8 core setup or 4 core 8 thread (hyperthreading) setup. This may be due to a lag time between new hardware introduction and drivers developed and optimized for said hardware.

Observation 1:
With a muti-monitor setup, I wanted to be able to see all instances of WoW on different screens. However, every time a WoW instance that crosses from one GPU zone to another GPU zone resulted in the WoW instance's graphic being software rendered instead of hardware rendered. Case in point, using the above example, if WoW1 which is seen on monitor B which is driven by GPU 0 and was to be click and dragged to either monitor C or D, would have resulted in the framerate dropping to below 10 fps. Moving it back to the original windows restored it to 60 fps.

To compensate for the above issue, I had to adjust when and where I loaded my WoW with which monitor and GPU. By adjusting the primary display in the vista display control panel solved this problem and ensured an equal GPU load balance on both GPUs. The techniques is as follows:

Load Sequence:
1) Primary display is set to monitor A or B.
2) Load WoW1 instance and display on monitor B.
3) Load WoW5 instance and display on monitor B.
3) Switch primary display from monitor A to monitor C or D.
4) Load WoW2 thru WoW4 instances on monitor C or D.
5) Switch primary display from monitor C or D to monitor A or B.
6) Use software to reposition WoW window instances. WoW1 and WoW5 on monitor B. WoW2 on monitor C. WoW3 and WoW4 on monitor D.
During the above load sequence, your WoW instances would be moved around due to changing primary display. Your mileage may vary on where they would finally end at, but executing step 6 would reposition the windows to their correct positions.

Observation 2:
For SLI, running 1 instance of WoW did not show any noticeable improvement and at times lowered performance. Running multiple WoW instances on SLI also resulted the same thing.

Observation 3:
In the memory bound section, using the first settings (high quality) for each respective WoW instance and testing it at Dalaran, my average fps for all WoW instances were between 10-15fps. The only thing noticeable was lowering the shadow quality improved average fps by 5 fps for each WoW instance.

7. PPU Bound:
Update in next revision.
8. AIPU Bound:
Update in next revision.
9. APU Bound:
Update in next revision.