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DMA Channel 2 is assigned to floppy Disk .
Which DMA Channel is an IDE Harddisk assigned to?

Can anyone give a short description how an harddisk driver does a DMA read/write ?

Thanks in advance!

Hi,

raywill wrote:DMA Channel 2 is assigned to floppy Disk .
Which DMA Channel is an IDE Harddisk assigned to?

The short answer is none, unless you've got an old XT. For more recent computers PIO is faster so they stopped using the ISA DMA. Since then they've added "PCI IDE accelerators", which is basically bus mastering PCI for hard disk transfers (which makes things a little messy considering the IDE/ATA controller is an ISA device for backward compatability purposes).

raywill wrote:Can anyone give a short description how an harddisk driver does a DMA read/write ?

IIRC it was "chipset specific", but Intel release a specification for bus mastering that most modern chipsets follow. According to this web page the specification is a de-facto standard called "Programming Interface for Bus Master IDE Controller Revision 1.0".


Cheers,

Brendan