Out of nowhere the processor utilization caused by DPCs on my box jumped from a few percent to 40%-50%, turning my PC into a very attractive boat anchor. The question was, why? What was causing this to happen? I never found an answer, and as mysteriously as the problem arrived it vanished.
While I was wrestling with the problem y'all suggested all sorts of potential causes, including faulty hardware (couldn't find anything and I hadn't changed anything), a misbehaving driver (why would one suddenly start causing problems and then stop?) and bad ju-ju. The last may be the best explanation of all.
I had several culprits of my own in mind, the most compelling being 's automatic update service, but the problem vanished before I could find any solid proof.
Reader Gary Lavery recently wrote to tell me about a similar mysterious problem where something was chewing up cycles on his PC, but unlike my DPC problem, Gary seems to have identified his gremlin.
Gary says that periodically his machine (a Inspiron e9400 laptop with XP Pro and 2 GB RAM) would freeze and the disk light would go on solid for 30 to 60 seconds.
To find out what was up Gary turned to , a freeware stay-on-top system monitor. Glint showed disk reads were the problem, but what process was responsible? For that he turned to Microsoft's freeware : that "showed unbelievable open, query, close cycles on WCESCOMM.LOG."
Not knowing what this file was, Gary searched and found it belongs to Microsoft's . "Ah ha!," he says. "I had installed [ActiveSync] to sync my phone remotely a long time ago, but it doesn't work when Outlook is hooked up over a VPN."
So Gary used the freeware to remove ActiveSync and voilà! His PC immediately started to behave itself.
Now Glint "showed very little activity, whereas it had been lit up like a Christmas tree previously," Gary says. "Filemon also showed very little activity, where before it had been overwhelmed with open, query, close cycles. These symptoms sounded similar to what you described for deferred procedure calls."
Gary noted that "the freeze ALWAYS occurred the first time a file was deleted. If you kept deleting files -- no freeze ups. But if you went on to other activities, then returned to Explorer to delete a file -- freeze! Likewise, the first e-mail opened in Outlook would cause a similar freeze. But subsequent opens breezed through. But if you switched windows and returned to Outlook, the first e-mail opened would cause a freeze. In all cases, the disk light was on solid and it would be 30+ seconds before you got the PC back. There's a clear pattern here. And it was repetitive -- not random. I could make the PC freeze at will."
Finally Gary says, "I don't really know what a deferred procedure call actually is -- but if this info helps for that reason or just in general -- please use it as you will. God knows you've helped me immensely with your column."
There may be some relationship between what Gary saw and my DPC problems, but I never noticed unusual file I/O activity. Ah, the wonders of Windows.
Back to a more recent topic: The whole cellular reception issue I wrote about and the has generated some interesting feedback.
Readers Jeremy Greenberg and (my favorite) A.N. Onymous wrote in to tell me about a new Web site that allows users to log their cell phone reception quality at any location and then shows it on a map. The site is and it is a neat idea, although its usability isn't great. Worth checking out.