The speed at which your hard drive transfers data is very important, right? Especially if you need to copy a 20-gigabyte file, like I did. My laptop was initially copying the file at 2 MB/s because it was transferring in PIO-only mode, which would have taken almost three hours. Not only is PIO terribly slow, it consumes lots of CPU power. While copying that 20-gigabyte file, my CPU usage stayed at 100%. Therefore, I tried to figure out the best way to increase the transfer rate. I changed the transfer mode to UltraDMA-6, speeding it up by 600% to 12 MB/s, and the 20-gigabyte file copied in a little over 30 minutes. Plus, my CPU usage was only about 20-30%.

So, how did the drive get lowered from UltraDMA to PIO-only mode in the first place? Well, because Windows has a particularly dumb way of handling transfer modes for storage devices. After six cumulative (all-time total) errors while reading or writing a storage device, Windows will automatically lower its transfer mode. Worse, it never goes back up unless you reinstall the device. This is bad if you put in a scratched CD, causing those six-in-a-lifetime errors happen all at once. Even your hard drive will experience an occasional hiccup, so eventually its transfer rate is not safe either.

However, there is a setting to force Windows to only lower the transfer rate after six consecutive (in a row) errors, and then raise it back up when the errors stop. Therefore, you can keep your drives in UltraDMA-6 mode.

If you would like to try changing the transfer mode for your drives, follow the instructions below. Going from PIO-only mode to UltraDMA-6 will show you the most significant performance boost. However, your results may vary. Of course, your drive and motherboard must support UltraDMA-6, or you won’t see much of a difference. Be careful while you are doing this; I am not responsible for any mistakes you make. Please back up your registry first in case something goes wrong!

How to Check Current Transfer Mode

1. Open Device Manager
2. Expand IDE ATA/ATAPI Controllers
3. Double click on Primary IDE Controller or Secondary IDE Controller
4. Go to the Advanced Settings tab to see the current transfer modes. If you see anything besides UltraDMA-6, and especially if you see PIO Mode, then follow the steps below.

How to Force UltraDMA-6

1. Open up the Registry Editor.
2. Navigate to the following key: HKEY_LOCAL_MACHINE\SYSTEMCurrentControlSet\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}.
3. There are several sub-keys under this one, such as 0000, 0001, etc. You are interested in two of them that say Primary IDE Channel and Secondary IDE Channel.
4. Make the following changes to both of those keys:
   1. Delete any attributes named MasterIdDataCheckSum or SlaveIdDataCheckSum. This resets the tracking for errors that Windows uses to determine when the transfer mode should be lowered.
   2. Add an attribute with the name ResetErrorCountersOnSuccess and a DWORD value of 1. This tells Windows that it should lower the transfer mode when there are six consecutive errors instead of six cumulative errors.
   3. If they exist, set the following keys to a hexadecimal value of ffffffff (eight F’s). This will change the transfer modes to UltraDMA-6:
      • MasterDeviceTimingMode
      • MasterDeviceTimingModeAllowed
      • SlaveDeviceTimingMode
      • SlaveDeviceTimingModeAllowed
      • UserMasterDeviceTimingModeAllowed
      • UserSlaveDeviceTimingModeAllowed
   4. Reboot your computer and check the devices to see if they are set to UltraDMA Mode 6.

[http://neodon.blogspot.com/2006/07/little-known-tweak-to-boost-hard-drive.html]