How to Fix IDE device using PIO mode instead of DMA

IMPORTANT: ** This is for EXPERT USERS ONLY. If you are not familiar with RegEdit and Device Manager, PLEASE don't follow these steps. Rather contact a computer expert that can help you!

** This has been test on WindowsXP Pro and Home SP1 and SP2 as well as on Windows 2003 and Windows 2003 SBS server. **


1 Start 'Device Manager' (Start -> Admin Tools -> Computer Management)
2 Open the 'IDE ATA/ATAPI controllers' folder.
3 Double click the 'Primary or Secondary IDE channel', select the Advanced Settings tab.
4 Verify that that mode is set to DMA, if not just change the mode to DMA and restart the computer (if the device is not in use this can take affect without a re-boot)

- If it is set to DMA but PIO mode is currently use follow these steps.

5 Delete both the 'Primary' and 'Secondary' 'IDE Channel'.
6 Start 'RegEdit' (Start -> Run -> regedit.exe)
7 Open key HKLM\System\CurrentControlSet\Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318}
8 Delete the sub keys 0001 and 0002 (these should be the primary and secondary IDE channels). If you want you can delete all the sub keys as the next re-start will auto detect the IDE controller as well as the IDE channels.
9 Restart the computer.
10 When you login to the computer please use a local Administrator login.
11 Follow the prompts on re-installing new hardware found.
12 When asked to restart you can ignore this for the time being as it will work fine without the restart.
13 To check that it is working: repeat steps 1 and 2
14 Double click the 'Primary or Secondary IDE channel', select the Advanced Settings tab.
15 Verify that that mode is set to DMA and that a DMA mode is the currently used mode.


I hope this has been to some help.

This problem is caused by Microsoft's atapi.sys driver that has a maximum hardware error count of 6. Once this number is reached the device will switch down to a slower mode (PIO in the end). There is currently no fix from Microsoft to fix this. However, if you have a HP/Compaq computer please search their KB and you will find an application that should fix the problem. If you don't have the correct computer you are wasting your time downloading this as it checks for the correct computer before installing.