I just came across this on a friend's PC and it occurred to me that many people might make this mistake: Without going into technical details, PCI latency is the time a device waits before returning focus to a device requesting it. Sound cards, USB ports and video cards all may all be connected through PCI latency settings. The lower the value, the faster focus passes between these devices. For flight simulator, you will want to give the video card a higher latency value, and 128 has been circulated for years now. Most systems ship with 32 as a default value. With 128, the video card has more time, more system resources, more CPU attention, and thus the simulator performs better. So far so good. I just found however that people seem to confuse PCI-Express with PCI. Some websites giving advice on latency settings also ignore the difference. PCI Express always has priority (hence the name Express) and does not have a Latency setting. It is not affected by the "PCI Latency" value in your BIOS, quite the contrary: If you have a PCI-e card and set your "PCI Latency" setting to a higher value, you are taking CPU cycles AWAY from the graphic card. The BIOS latency setting refers to all other devices on the bus BUT NOT a PCI-e card. You should set your PCI Latency to the lowest value available, if you have a PCI-e adapter. Note that AGP slots DO use PCI Latency, so there you want a higher value. There's a tool on 3dguru.com to list the latency values of all PCI devices in your PC. If that tool has no graphic card on the list, you don't have a PCI card. Alternatively, look for tools like cpuz (http://www.cpuid.org/cpuz.php) - or other system information tools - they usually list the type of slot of your video card. Also, note that if you have your system overclocked - motherboard, memory and CPU, the higher you overclock the more important the correct PCI Latency setting becomes. Roughly speaking higher clocks necessitate lower latency setting. Setting higher latency values for a device may cure stutters. If you have sound problems, try to give the sound card more latency, if you have video stutters, give the video card more latency.

Thank you for this one-I changed from 32 to 128 and saw a nice improvement!edit-and a little later I set it to the max my bios supported-and even saw more improvement! Something to definately check out-thanks again!http://mywebpages.comcast.net/geofa/pages/rxp-pilot.jpg

Yeah, same here,noticed a nice performance boost! I've always been a bit apprehensive about OCing but this seems stable enough. Thanks!

I have 248 by deafult, any suggestion?

I think most ATI based cards defaulted at 255, and the idea was to reduce that.scott s..

you have to be more precise ... 248 for the PCI bus with a PCI video card? or a PCI-e card??PCI card: you are giving all the power to the card. if your system is stable, great. watch for sound problems if using a PCI sound card, it will likely be a problem. PCI-Express: you are starving your video card of resources

When the latency issue first came up a few years ago, the common wisdom had it that 64 was the holy grail setting. that is what I have been using, until now. after reading this thread, I upped it to 128, with very good results, and then to 256...again, very good results. there is now little or no lag on scenery tiles when I switch views. I have an nvidia 7600GS (agp) with 512 megs of ram on board. My mobo is an asus oc'd to 3.12 mgh with 1 gig of system ram. i run at a fixed rate of 25fps in fs9, few if any blurries. when they do occur, they are only momentary. stutters are virtually nonexistent.Sherm