These links are collected from articles about troubleshooting audio performance issues in Vista:

http://www.thesycon.de/deu/latency_check.shtml

According to posters on the Project BarBQue mailing list, one of the primary performance metrics is the time spent at "DPC level", a driver dispatch level where access to system resources is first come, first served. If a lot of time is spent at DPC level, it affects the entire system. USB and firewire audio devices often have very tight timing margins, where their drivers must respond to interrupts within a very narrow
time interval. If *anything* else is running at DPC level when they need this timeslot, you'll get glitches.

DPC Latency Checker is a Windows tool that analyses the capabilities of a computer system to handle real-time data streams properly. It may help to find the cause for interruptions in real-time audio and video streams, also known as drop-outs.

RATTV3 is a tool for auditing the execution times of interrupt service routines (ISRs), deferred procedure calls (DPCs), and timer DPCs on systems that are running Windows XP. RATTV3 is designed to help developers of drivers and other kernel mode components audit the ISR and DPC execution time of their components.

http://technet.microsoft.com/en-us/sysinternals/bb896653.aspx

The unique capabilities of Process Explorer make it useful for tracking down DLL-version problems or handle leaks, and provide insight into the way Windows and applications work. You can use it to see what % of the CPU is being devoted to DPCs that might be causing audio glitches.

http://www.focusrite.com/answerbase/article.php?id=265

Use the described tool to track down any devices on the PCI bus that have high PCI latency timer settings. The tool displays the current latency values for all expansion devices on the PCI bus and allows you to set the values manually. If you are experiencing clicks and pops and audio glitches on your PC and your graphics card or network card displays a high latency with this tool, try reducing the latency to 128 or 64 to stop hogging the bus. If you are using a firewire audio interface, you might also try increasing the Latency Timer value of your Firewire controller.

For end users needing maximum CPU cycles and RAM for audio, this free command line process utility can be used to create a batch file that kills all but necessary programs.

Tom White
AMP Alliance