DMA

Direct Memory Access
The advantage of using Direct Memory Access (DMA) with IDE CD-ROM and disk drives is that it lowers CPU usage during I/O transfers. This drastically improves performance when using these devices.

Ensure that your drive supports DMA before making these changes, otherwise it could lead to unpredictable results. To use DMA:

1. Open Control Panel > System > Device Manager.

2. Click the + sign next to the Disk drives entry.

3. Select the drive you want to enable DMA for and click Properties.

4. On the Settings tab, there should be a DMA check box. You can enable this to enable DMS for the drive.

Note: If there is no check box (or it is greyed out), your motherboard chipset does not support the feature. If the check box is not checked after you restart your system, your hard disk probably has been automatically disabled again because the hard disk may not support DMA. If you are unable to restart Windows after the change is applied, boot to Safe Mode and disable DMA from here.

Stands for "Direct Memory Access." DMA is a method of transferring data from the computer's RAM to another part of the computer without processing it using the CPU. While most data that is input or output from your computer is processed by the CPU, some data does not require processing, or can be processed by another device. In these situations, DMA can save processing time and is a more efficient way to move data from the computer's memory to other devices.

For example, a sound card may need to access data stored in the computer's RAM, but since it can process the data itself, it may use DMA to bypass the CPU. Video cards that support DMA can also access the system memory and process graphics without needing the CPU. Ultra DMA hard drives use DMA to transfer data faster than previous hard drives that required the data to first be run through the CPU.

In order for devices to use direct memory access, they must be assigned to a DMA channel. Each type of port on a computer has a set of DMA channels that can be assigned to each connected device. For example, a PCI controller and a hard drive controller each have their own set of DMA channels.