I don't really know if this the correct forum to post my question co'z it doesn't seem to fit into any categories but anyway...

My modem (acer netxus 56k internal) has a pci latency of 248; it hogs the pci bus too long. What are the other bad side-effects of having a high latency?

What should be the optimal or best latency for my modem? ; and how could I change it? What prog should I need?

Well to be simple and precise,
If the latency timer is set too low, PCI devices will interrupt their transfers unnecessarily often, hurting performance. If it's set too high, devices that require frequent bus access may overflow their buffers, losing data.

There maye be lot of other devices in your system that access the PCI bus like, Sound cards, Video cards, NIC cards. If the PCI Latency timers of these devices are high in variations, eg NIC 32, Sound card 64, Modem 248, then the NIC card and Sound card are likely to hog the bus and make it difficult for the Modem to keep up with the load. So u may experience frequent pauses, un-wanted lock-ups and other problems related to the respective devices.

I would suggest you to set the timer from min 32 to max 64 for PCI devices. Try to avoid extreme variations.

Well, How do u set it? Its not that easy I guess, for Video Cards you can use power strip I guess. For others I don't know any device specific utilities. But there is something called TweakBIOS that can do it for any device, its not a freeware though. And it works in DOS, Win9x systems only, it may work in nt based systems like NT,2K,XP but its a bit tricky becuz NT based system do not use real DOS. With the shareware version you can change many other Configurations including latency timers but you won't be able to save them and make the settings load at each boot.

Hope this helps.

for Video Cards you can use power strip I guess. For others I don't know any device specific utilities

Actually, PowerStrip (http://www.entechtaiwan.net/ps.htm) can adjust the latencies for any add-in PCI card. Just right click on the powerstrip tray icon, go to Options>Adapter Information. At the top right corner of the Window there is a set of up and down arrows. Using these you can cycle through all of the devices on the PCI bus. For each one there is a section for "Latency". Onboard devices will be greyed out, as they are controlled by the BIOS entirely. Add-in cards, however, are allowed to set their own latency.

Make sure the check box for "read only" near the bottom right of the window is unchecked.

My video card has set itself at 248, my sound card at 32, my TV Tuner card at 32, my nic at 32. I haven't adjusted these, as I haven't experienced any problems.

Try bringing your modem down to between 64 and 128.

Although Powerstrip can be installed and used for free indefinitely, if you decide to keep it, buy it. It's a nice utility and they update often.

Good luck.:)

Edit- I should add that if you are not experiencing any specific problems then don't worry too much about the latency. Only adjust it if you feel it may resolve these problems(if any).