First suggestion. Google is your friend. Takes much less time to find the answer yourself than wait for a response from someone on the boards.
FYI DMA isn't exlusive to Windows XP. Short answer is that it's a less CPU intensive method of moving data from a device into the computers memory. It bypasses the CPU and goes direct into the memory, unlike PIO which brings the CPU into the loop... which isn't a good thing as it wastes cycles.
Direct Memory Access
Direct Memory Access (DMA) is a capability provided by some computer bus architectures that allows data to be sent directly from an attached device (such as a disk drive) to the memory on the computer's motherboard. The microprocessor is freed from involvement with the data transfer, thus speeding up overall computer operation.
Usually a specified portion of memory is designated as an area to be used for direct memory access. In the ISA bus standard, up to 16 megabytes of memory can be addressed for DMA. The EISA and Micro Channel Architecture standards allow access to the full range of memory addresses (assuming they're addressable with 32 bits). Peripheral Component Interconnect accomplishes DMA by using a bus master (with the microprocessor "delegating" I/O control to the PCI controller).
An alternative to DMA is the Programmed Input/Output (PIO) interface in which all data transmitted between devices goes through the processor. A newer protocol for the ATA/IDE interface is Ultra DMA, which provides a burst data transfer rate up to 33 MB (megabytes) per second. Hard drives that come with Ultra DMA/33 also support PIO modes 1, 3, and 4, and multiword DMA mode 2 (at 16.6 megabytes per second).
Last edited by tazdevl
on Thu May 01, 2003 9:18 pm, edited 1 time in total.
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