11 Facts About DMA channel

Many hardware systems use DMA channel, including disk drive controllers, graphics cards, network cards and sound cards.

DMA channel is used for intra-chip data transfer in multi-core processors.

DMA channel can be used for "memory to memory" copying or moving of data within memory.

DMA channel is of interest in network-on-chip and in-memory computing architectures.

Once the DMA channel controller is granted access to the system bus by the CPU, it transfers all bytes of data in the data block before releasing control of the system buses back to the CPU, but renders the CPU inactive for relatively long periods of time.

Related searches

The primary advantage of transparent mode is that the CPU never stops executing its programs and the DMA channel transfer is free in terms of time, while the disadvantage is that the hardware needs to determine when the CPU is not using the system buses, which can be complex.

Non-coherent systems leave this to software, where the OS must then ensure that the cache lines are flushed before an outgoing DMA channel transfer is started and invalidated before a memory range affected by an incoming DMA channel transfer is accessed.

Particularly, the advent of the 80386 processor in 1985 and its capacity for 32-bit transfers, as well as the development of further evolutions to or replacements for the "ISA" bus with their own much higher-performance DMA channel subsystems made the original DMA channel controllers seem more of a performance millstone than a booster.

Each DMA channel has a 16-bit address register and a 16-bit count register associated with it.

Internally, a multichannel DMA engine is usually present in the device to perform multiple concurrent scatter-gather operations as programmed by the software.

The DMA channel command is issued by specifying a pair of a local address and a remote address: for example when a SPE program issues a put DMA channel command, it specifies an address of its own local memory as the source and a virtual memory address as the target, together with a block size.