*Updated - 4/17/09* New drivers from Intel as provided by Anonymous
*Update* I tried out the DPC latency tool recommended by Martin. Here's a screen cap of how much the latency drops if you just physically remove the CD/DVD drive.
(the additional spike afterward was just me opening SnagIt). It's obscene.
Update 2: Please see Martin's post in the comments section below for additional remediation steps.
Update 3: The Dell tech recommended switching the SATA mode in BIOS from IRRT to AHCI. Of course, if you do that you've got to completely reload your Operating system. I tried it on a spare drive with a fresh install of Vista 32 bit and I haven't had the audio skip yet though I'm still loading more apps on it to test with. The latency was still high but didn't appear to affect audio playback which seemed odd.
Update 4: I Disabled the eSATA port under BIOS and the latency issue with the DVD drive plugged in went away. (For a whole reboot) This just keeps getting better.
So I noticed that the E6400 was having weird audio glitches with Vista while under light loads. It was behaving like the hard drive was under heavy load and interrupting the data transfer. But all the resource monitors only showed minimal load. I ran into this problem with all mp3 files and I tried just about everything on the help forums including a fresh load of XP and Vista respectively on a different hard drive. I tried turning off sound effects, changing power saving, turning off wireless, etc.
The solution: The latest Intel Matrix Storage Manager driver! While trying to fix a problem with DVD burning, I ran into a suggestion on the forums related to the SATA controller. After installing the latest driver I went ahead and tested the audio again and the darn thing works perfectly now. My guess is that the previous sata driver wasn't stable enough and was causing the audio problem as a side effect.
Release Date: 1/8/2009
Version: 18.104.22.1687 Other Versions
Download Type: Application
File Format: Hard-Drive
File Size: 21 MB
Granted, if I push it hard enough I can still make it skip once in a while but it takes a lot of effort. Whereas previously I could do it with freecell.