UDMA66 on Intel Chipsets

[Ascii2]

Interesting, I’ve never tested it. This computer is an adequate web surfer so I haven’t bothered to pursue the UDMA 5 glitch. Does anyone know of a reliable utility (preferably freeware) to find out if it is the motherboard bios or XP that is in error?

You may try Hd Tach 3.0.4.0 to run a benchmark on the hard disk and examine the burst speed value. If the burst speed value is greater than 66.7 MB/s Ultra DMA Mode 4 is being exceeded; if it is not, either a DMA mode lesser than the greatest possible of the drive is being used, or (less likely) the hard disk is not capable of making enough data available for higher transfer rates.

If Ultra DMA 4 is being exceeded, it is Windows XP that misreports the transfer mode.

HD Tach 3.0.4.0 (freeware) may be downloaded at:

http://www.simplisoftware.com/Public/index...?request=HdTach

Edited November 30, 2008 by Ascii2

[Sysdll]

Thanks for the link. On this machine with XP reporting UDMA 4 the average read is 44.8 mb/s and the burst is 56 mb/s. I also ran it on another machine with a promise controller and the average is 30 mb/s and the burst is 88.6 mb/s. With the programs I have I can’t see a difference.

I’ve had a lot of computer malfunctions caused by my fixing something that really didn’t need to be fixed so I’ll leave it alone.

[Ascii2]

I *think* (after all, I'm not an insider) it enables, but not restricts to.

I have been able to test the EnableUDMA66 value affect on a computer using a Intel chipset and an IDE hard disk capable of transfering at rates greater than UDMA66. The hard disk was still able to transfer at rates greater than UDMA66 after applying the UDMA66 set to 1 registry modification.

I noted a burst spped performance increase for the hard disk of about 6.25% after enabling the UDMA66 setting (only ran a benchamark a single time to test).

[cluberti]

They were probably so thrilled they got it working that they forgot to assume that higher speed will appear.

Whilst you might think that your snark is well placed, remember that this fix was initially introduced in December 1999 for Windows 2000, when the UDMA4 standard was actually ratified. UDMA5 wasn't ratified until early 2002, which was after XP released in October of 2001. Note that at least officially, XPSP1 and up include support for UDMA100 if the chipset drivers allow it, and I don't think that was ever increased when UDMA6 was ratified later in 2005.

I don't know why people think this stuff has been around forever, when in reality UDMA4 wasn't ratified until 2000, UDMA5 until 2002, and UDMA6 until 2005.