Hard Drive "Direct Memory Access" Modes

One of my friends, fellow pc experimenters and Terry's Computer Tips Newsletter subscriber Ron Spruell was having hard drive problems recently.

One of the problems was that a hard drive that, according to the hard drive manufacturer and the motherboard manufacturer, should have been running in DMA5 mode was instead running in DMA2 mode.

While talking with Ron, I suggested that he go into the Device Manager and "uninstall" (at least as far as the Windows Registry was concerned) the hard drive in his computer.

When Windows has problems reading a drive, after a certain number of errors, it will "downgrade" the interface from DMA5 (the fastest). He was at DMA2.

I've fought that problem before and successfully resolved it by "uninstalling" the hard drive. Of course, the next time Windows XP boots, it finds a "new hard drive" and sets it up properly as DMA5 for the Direct Memory Access controller. This made a huge difference in the effective speed of my hard drive.

However, Ron's problem turned out to be something else:

I tried your suggestions of uninstalling the hard drives. I also uninstalled the IDE Channels. That did not fix the problem.

I was reading the Motherboard users manual (imagine that). I found, in BIOS settings under IDE Configuration:

"The P-ATA+S-ATA and P-ATA options are for advanced users only. If you set to any of these options and encounter problems, revert to the default setting S-ATA."

My setting was P-ATA+S-ATA. I changed it to S-ATA. That solved the problem. I am now running UDMA Ultra Mode 5.

I'm glad you got the problem solved, Ron. Thanks for sharing the knowledge with us. I'll tuck that experience away in my brain so it can help me with a similar problem one day.

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