Specifications

Enabling the DMA Mode

DMA mode - Direct Memory Access - allows certain hardware subsystems within a computer to access system memory for reading

and/or writing independently of the CPU. Many hardware systems use DMA including disk drive controllers, graphics cards, network

cards, and sound cards.

DMA is an essential feature of all modern computers, as it allows devices of different speeds to communicate without subjecting the

CPU to a massive interrupt load. Otherwise, the CPU would have to copy each piece of data from the source to one of its registers,

and then write it back again to the new location. During this time the CPU would be unavailable for other tasks.

A DMA transfer essentially copies a block of memory from one device to another. While the CPU initiates the transfer, the transfer

itself is performed by the DMA Controller. A typical example is moving a block of memory from external memory to faster, internal

(on-chip) memory. Such an operation does not stall the processor, which as a result can be scheduled to perform other tasks. It is

essential in providing so-called zero-copy implementations of peripheral device drivers as well as functionalities such as network packet

routing, file copy, streaming video over a network, etc.

enable the DMA mode you should do the following:

1. Go to the Windows Start menu and select Control Panel;

2. In the Control Panel window choose the System icon, double-click it to open the system properties window;

3. In the Hardware tab there is a Device Manager button:

You should click it to open the Device Manager window:

AVS4YOU Programs Help - Appendix

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