Bij Tweak3D is een artikel verschenen waarin wordt uitgelegd hoe Bus Mastering, PIO en DMA mode transfers werken. De logische conclusie van het artikel is dat hardware dat direct kan worden aangesproken meestal een betere performance geeft:
The highest performing DMA type is called first party or Bus Mastering DMA. Peripheral devices, which support the Bus Mastering technology, have the ability to move data to and from system memory without intervention of the CPU or a third party DMA controller.
Bus Mastering allows data to be transferred much faster than PIO or third party DMA. This is because half as many bus cycles are needed. Both PIO and third party DMA require the CPU or DMA controller to alternately read a segment of data from one device (this can be the a peripheral device or system memory) and write it to the other device. Each data segment requires at least one bus cycle to be read and one bus cycle to be written. Bus mastering devices only require bus cycles when accessing system memory, so half as many bus cycles are needed. As a bonus, system memory can be accessed using high-speed transferring techniques such as page mode access.
Because of this, devices that support Bus Mastering can move data many times faster than either PIO or third party DMA. Bus Mastering controllers typically support Command Queuing and Scatter/Gather memory access, which greatly increase performance in multi-user environments like Windows NT/2000, UNIX/Linux and Novell.
DiederikJ bracht ons op de hoogte.
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