Monday, March 23, 2009

COMPUTERS - Video, Sound, and PCI Latency

There is an on-going problem with video and sound, especially with games.

The issue is bad/choppy sound or even lockups when playing games. This MAY be very apparent when you have a Creative Labs sound card (even the FX model).

The cause is usually a clash between your system accessing the video and sound cards, which tend to be fast and furious during game play. Both devices use much resources when sending/receiving data, especially at today's high speeds.

The problem resides in what is known as PCI Latency (see applicable paragraph Auto Configuration in article).

PCI Latency is a function of how long any PCI device holds open access to the bus before passing on to the next device, and is handled by the BIOS. Some, but not all, devices have a means to program the latency timing (in multiples of 8).

Problems are caused by the PCI Latency timings for video and sound cars being too close together. This is, the video card still needs to process data but the bus gets released to the sound card, or visa versa.

The fix is to set the PCI Latency timings at LEAST 8 apart. That is the PCI Latency for the sound card at least -8 of the video card. On my home PC, all PCI Latency = 56 as set by the BIOS. This resulted in very choppy sound including pops & clicks.

I found one way to fix this, the PCI Latency Tool.

You install this tool, change the sound card latency, then apply and SAVE. Saving the setting will reload your settings on bootup. Make SURE you read the instructions for this tool.

CAUTION: DO NOT move or rename the [Start], Programs, folder the PCI Latency Tool is installed in.

On my home PC, I used this tool to set the latency for my sound card to 48:
  • Video = 56 (BIOS default)

  • Sound = (56 - 8) = 48

As a result, I get very, very little chopping/popping. And IF I do, it is very low volume.

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