By default, slave drives on ATAPI or EIDE channels are often set to PIO mode, which can slow the performance of a drive, CD-ROM, etc. By offering them DMA if it is available, then you can speed up your drive.
First of all, what is PIO?
PIO stands for Programmed Input/Output, a method of transferring data between two devices that uses the computer's main processor as part of the data path.
Modes are 0 through 4:
Data Transfer Speed
If Ultra DMA is used, then speed is enhanced depending on the speed of the drive and controller, Ultra/33 runs at 33 Mbps and so on up to Ultra/133. Follow these steps to assign a DMA value if available:
Click on Start button
Settings, Control Panel
Double click on System Properties
Select the Hardware tab, and click on Device Manager for Win 2000 and XP.
Expand the entry for IDE/ATAPI controllers.
Right click on the Primary Channel first and select Advanced Settings tab.
For each device listed, change the transfer mode to "DMA if possible or DMA if available."
Repeat the same for the Secondary Channel and then Restart system.
Note: Don't worry, devices that are not capable of DMA mode will still work just fine. You should see some speed increase now if your devices are using DMA. Just remember that DMA lets the controller talk to the device attached without going through the CPU so it frees up some CPU resources.
Extracted from Extreme Tech with additional comments from myself.
Just click on the button to access my home page. Just click on the CD for the Hardware Tip Page.