Warning: This is a fairly technical discussion that will probably not be of interest to Mom.
A few times lately I have struggled with people’s computers trying to find out why they are running so sluggishly. When no programs are running, Task Manager shows the CPU usage at 50% – 80%, though the process list doesn’t show anything using any of that processing power. Normally, CPU usage should be between 0% and maybe 4% when idle (at the bottom of the Task Manager window.) I thought at first that there must be a hidden virus, or rootkit running in the background. But I was wrong.
What happens is that the hard drive is not being accessed in fast DMA mode, but rather in a much slower PIO mode. Windows monitors hard drive errors, and when they reach a certain level it assumes that the drive can’t handle DMA and switches it to PIO. Usually the hard drive can still run in DMA just fine.
Check it out in Device Manager. Look under “IDE ATA/ATAPI controllers” at the “Primary IDE Channel”. In Properties, on the Advanced Settings tab, “Current Transfer Mode” should be “Ultra DMA Mode” or something that has the word “DMA” in it.
If it has fallen back to PIO, the solution is to uninstall the Primary IDE Channel in Device Manager, then reboot. The system may require a second reboot, but in the end it will reinstall the controller, usually back in DMA mode. It will make a huge difference in your performance.
7 responses so far ↓
1 Donna // Aug 4, 2007 at 3:03 pm
How do I find Device Manager?
I’ve had lots of Firefox crashes lately. It says Firefox has performed an illegal operation. It seems to be mostly when I try to launch videos. If they weren’t from trusted sources, I’d suspect viruses, but even a QT video on apple.com continually crashed Firefox today. Anyone else have this problem?
2 Grandma // Aug 5, 2007 at 9:46 am
Not to change the subject (I was VERY interested in the DMA and PIO), but when can we expect a new picture of Apollo?
3 Daryl // Aug 5, 2007 at 10:07 am
To find Device Manager: Right click on My Computer and select “Properties”. Then select the Hardware tab, and click on “Device Manager”
Donna, it sounds like maybe you need to update your Quick Time. Also, make sure you are using Firefox 2.0.0.6.
Of course, check for the usual suspects; viruses, trojans, spyware etc.
4 Daryl // Aug 5, 2007 at 10:09 am
Mom — I’m working on a picture of Apollo. I want to get one of him in his working harness, pulling the “sled”.
5 Donna // Aug 5, 2007 at 9:05 pm
I checked mine out, and it’s Ultra DMA mode, so I guess it’s fine. Thanks!
6 Heather // Aug 6, 2007 at 5:53 am
My device 0 is on Ultra DMA mode, but device 1 is on PIO.
Should I change anything?
7 Don // Aug 6, 2007 at 7:06 am
You might want to put device 1 on auto Heather. Windows 2000 has that setting. I’m sure your device 1 is the DVD so it’s not as critical as the hard drive. The DVD can’t get data on and off near as fast as a hard drive so PIO is probably not hurting you but it doesn’t hurt to put it on auto.