[wdmaudiodev] Re: removing working USB soundcards cause the System hangs

  • From: Tim Roberts <timr@xxxxxxxxx>
  • To: "wdmaudiodev@xxxxxxxxxxxxx" <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Tue, 13 Sep 2011 09:42:42 -0700

> I have a very difficult problem with USB audio devices on WindowsXP.
> I have many(up to 16) USB soundcards (based Micronas UAC3556b) working 
> simultaneously. For low latency I used the DirectKS.
> When I connected the devices through USB2.0 I got the high CPU usage (up to 
> 100%) in the DPCs of the System process. So, I disabled Enhanced USB 
> controller, soundcards reconnected to the 
> USB universal host controllers and the CPU usage went down to ~15%.

Are your able to change the descriptors for your device?  If you change
the "USB version" field in your descriptors from 0x0200 to 0x0110, then
the operating system will automatically assign you to a UHCI virtual
controller instead of an EHCI controller.

(I just looked at a UAC3556B datasheet, and it looks like this is not
one of the fields they expose.)

> Now I have another problem.
> Removing the working soundcards cause the 100% CPU usage in the System 
> process. The Windows hangs up.
> if I connect soundcards to USB2 controller (the lower count) I can remove the 
> working soundcards and Windows doesn't hangs.

USBAudio.sys is a very complicated piece of software.  It's quite
possible that the XP version has some surprise removal problems in
certain unusual cases.  Have you tried this on Windows 7?  You aren't
going to get anyone interested in fixing problems in XP.

Tim Roberts, timr@xxxxxxxxx
Providenza & Boekelheide, Inc.

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