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I'm just playing around with the QEMU system emulator, and taking a look at the IDE disk emulation, specifically at the DMA disk accesses.

I'm a little confused as to how DMA requests are actually addressed.

For example, the first DMA request made by the OS is to sector zero.

Now on the physical disk, sector zero is the MBR, however on the logical disk, sector zero is the volume boot record.

So my question is this; when Windows, or any OS for that matter makes a DMA request to the disk, is it addressing a logical partition, or the physical disk?

I hope that makes sense!

nc4pk
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Tony
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1 Answers1

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You're question is a little unclear, as I think you're misunderstanding what DMA is.

DMA isn't making requests to the disk, it's providing Direct Access to the Memory instead of going to the CPU first.

Since DMA is a hardware-level data transfer method, then as long as the drive, HDD controller, MB, driver and OS all support DMA transfers, the file-system on the drive doesn't matter.

More info:

Ƭᴇcʜιᴇ007
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