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Comment: Re:That speed comes at a cost (Score 5, Informative) 280

by Vihai (#26402081) Attached to: USB 3.0 Is Ten Times Faster; Get It In 2010

USB is PIO and not DMA? You understand that PIO/DMA transfer modes only meaningful for Parallel ATA devices?

That's because the ATA interface was originally THE 16-bit system bus (AT bus) and the disk controller was onboard on the disks (thus the name IDE - Integrated Drive Electronics).

So, the CPU accessed the disk controller through the AT bus which was originally programmed I/O and then started using DMA.

Of course, the system bus quicky become different and faster (FSB + PCI) thus the ATA interface became a disk attachment interface instead of the system bus and an additional controller was put between the system and the disk.

USB is a completely different beast. The "bus" actually transfer packets (URBs) and all USB controllers use DMA to transfer URBs to the main memory... So, no PIO/DMA stuff is involved....

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