Almost impossible to max out bus. Gathering real-time data on 1000 issues will usually run only about 100KB/s* data stream.... .maybe 5X that in a panic?. Even an x1 card can handle 500MB/s. * That's with eSignal. I don't know whether their data is every tic or perhaps they just report every 1/10 second or something. There are data monitoring utilities you can run to check bandwidth throughout the day if you have any doubts.
Can't see that making any difference at all. You could run a quad port card from an x1 slot without any negative impact... at least not until the data stream >500 MB/s.
I answered this with a couple of posts above. I'm running 2 monitors from an x1 card.. can't tell any difference (nor should there be) from the x16 cards. That you're "performance suffered [with 5th card]"... highly unlikely it has anything to do with video bandwidth. The more monitors you have you COULD run more data, of course, if you had it. However, the reality is that you're currently dividing your present data bandwidth among all of your monitors. Your present rig isn't running at even 1/10,000 of it's max capability.
You say your cards are GeForce 8200 GS. I can't find tech specs on them or even confirmation that's a valid model number. Are you sure that's the card you're using? Is this a 2D or 3D card? And what does the card tech specs say about min bus speed?
ATI PowerColor 5770 Eyefinity 5. Powers 5 monitors with 1gb ram. Two of them run 10 monitors happily. if this is related to the number of cards (and the age) then this may be a solution.
Scataphagos is right. I am so sorry. I messed up on typing the model number. They are: 8400 GS, made by EVGA, 512MB onboard RAM, PCIe V2.0 The very clear symptom to me is: 4 of such cards, everything happy. Added the 5th card, everything went to hell. Windows spent >20% of CPU time just tracking the mouse movements. Running TradeStation pushed the CPU usage to over 80% constantly. My test was: normally my TradeStation layout takes about 3 minutes to come up (with 4 cards). With 5 cards, it took 20 minutes to complete. Kind of like watching the window populating in slow-mo X5. Something is obviously wrong with that config. I just couldn't quite figure out what it was. The only thing so far led to that when the fifth card was brought in, all bus bandwidth will be at X4 speed per documentation from MSI on the motherboard.
Most likely something about that 5th video card and your mobo/OS (perhaps flash the BIOS with an update??). Even with each video card running "only 4x", that can still handle 10 GB/s data stream.... and no trading multi-tasking data are within a light-year of that.
@ Scataphagos: What x1 card are you using, and is this in conjunction with another card/cards? Knowing you're a NVS 295 man, can I assume a combination of these?