Tuesday, January 20, 2009

Enable your computer's DMA

Direct Memory Access (DMA) is a technique that hard disks and CD-ROM drives can use to transfer data directly to and from memory, without passing through the processor. DMA reduces the load on the system processor since data transfers do not require monitoring by the CPU. With DMA, a write or read operation can be executed in two to four clock cycles. Without DMA it will cost the CPU a minimum of 16 clock cycles per operation. Not only do disk read/write operations gain a significant boost in speed, but Windows also works faster, since it can load system files much faster and also accesses the swap file at higher speeds. Older hard disks and CD-ROM drives do not support DMA, but almost all computers today use DMA-compliant devices. In case you face a problem after enabling DMA, reboot Windows to Safe Mode and disable the option. Also, DMA needs to be enabled from the BIOS, but again, on most computers, this is on by default. DMA is supported only in Windows 95 OSR 2 and later. To enable DMA, open Control Panel > System > Device Manager.Expand the Disk drives tree, select the hard disk and click Properties. Under the Settings tab, check the DMA option. Repeat this for all other hard disks and the CD-ROM or DVD-ROM drives.