Coding Horror: Transfer Mode Downgraded

September 4, 2006

Transfer Mode Downgraded

I noticed when I was burning the Vista RC1 DVD that ..

It took forever, eg, nearly an hour
My PC was very sluggish during the burn

I began to suspect something was awry with the IDE controller that the DVD-R drive is connected to. I navigated to Device Manager, expanded the IDE ATA/ATAPI controllers tree node, right-clicked the Parallel ATA Controller node and selected properties.

And what do I find on the Secondary Channel tab? Sure enough, Transfer mode downgraded.

Transfer mode downgraded: the transfer mode for this device was set to a mode lower than what it is capable of because of excessive transfer errors to the device. This will cause a loss of system performance. Please check the cabling to the device and verify an 80 conductor flat ribbon cable is used for Ultra66 and higher transfer modes.

This behavior is, of course, by design. Microsoft automatically downgrades the transfer mode on a Parallel or Serial ATA channel after receiving more than six CRC errors on that channel. At least you can see when this has happened-- Microsoft provides the little yellow alert pictured above, along with some alerts in the system Event Log.

CRC errors are very dangerous for a hard drive-- that means you've got some serious hardware problems. But for a DVD or CD drive, it probably just means you tried to read a scratched disc. You can override this obnoxious behavior in the registry.

I flipped the switch back to "Let BIOS select transfer mode", rebooted, and I was on my way:

BIOS-selected Ultra DMA 2 transfer mode for a DVD/CD-ROM

However, depending on what Windows XP has decided to do here, you may need to uninstall the channel (just right-click it in Device Manager to do this). Don't worry, uninstalling won't cause any problems. Just reboot and the channel will be redetected with default settings.

To illustrate how important proper PATA/SATA transfer mode settings are, here's how long it took to burn a Vista RC1 DVD on my PC before and after:

in PIO mode: 56 minutes.
in Ultra DMA 2 mode: 4 minutes.

Friends don't let friends use Programmed I/O Mode.

Posted by Jeff Atwood View blog reactions

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Comments

There's another nice set of info and workarounds on the CD/DVD-ROM transfer mode problem here:

http://users.bigpond.net.au/ninjaduck/itserviceduck/udma_fix/

Jeff Atwood on September 5, 2006 12:27 PM

Interesting looking IDE channel config box. It's obviously not what's in the hardware manager; is it some nifty tool you're going to share with us all?

Foxyshadis on September 5, 2006 6:14 PM

Hmmm... I ran into something similar a couple of days ago.

http://west-wind.com/weblog/posts/7246.aspx

So did this occur on Vista for your or on XP?

I checked my settings in Vista and the dialogs don't allow these options, but I do see DMA Mode enabled on both devices.

Rick Strahl on September 5, 2006 11:12 PM

"Interesting looking IDE channel config box. It's obviously not what's in the hardware manager; is it some nifty tool you're going to share with us all?"

I get those exact screens here on a vanilla XP install and turns out I had the same issue. Did you follow his directions for getting there?

Nick on September 6, 2006 4:33 AM

I have XP Pro SP2 on a PC with a motherboard-integrated Intel Ultra ATA controller, and Device Manager -> IDE ATA/ATAPI controllers offers nothing like this. I can't see any way to determine or change the transfer mode at all. There is no dialog with a "Secondary Channel" tab.

It may be that the drivers for some controllers offer features that others do not.

Western Infidels on September 6, 2006 8:19 AM

I believe the dialog pictured is based on the nVidia nForce chipset drivers..

I just checked on a web server here, and I see a similar (though not identical dialog) under the Primary IDE Channel. In the properties dialog for the Primary IDE Channel there's an "Advanced Settings" tab which has the current transfer mode and a drop-down menu which lets me change the DMA mode.

That's based on the "Intel 82801EB Ultra ATA Storage Controllers".

Jeff Atwood on September 6, 2006 9:31 AM

I think it was 2000 where PIO was selected by default on CD-ROM drives.

Philihp Busby on September 6, 2006 11:50 AM