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 Post subject: Relation between DMA and AHCI technologies
PostPosted: June 15th, 2011, 5:16 
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Joined: June 15th, 2011, 5:12
Posts: 1
Location: Chennai
Hello Everybody,
AHCI is defined as "a data movement engine between Memory and SATA devices". So DMA also acts as a "data movement engine between memory and storage devices". So, Is AHCI is enhanced version of DMA? Can anybody give me more clarification on this?

Thanks
Aariyan


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 Post subject: Re: Relation between DMA and AHCI technologies
PostPosted: June 15th, 2011, 5:25 
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Joined: July 21st, 2010, 5:03
Posts: 247
Location: Norfolk, UK
I believe that AHCI enables NCQ support as well as hot-plug capability, Performace difference is negligible..

Steve..

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 Post subject: Re: Relation between DMA and AHCI technologies
PostPosted: June 15th, 2011, 5:37 
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Joined: September 29th, 2005, 12:02
Posts: 3577
Location: Chicago
DMA is a protocol
AHCI is an interface

They not comparable

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 Post subject: Re: Relation between DMA and AHCI technologies
PostPosted: June 15th, 2011, 9:22 
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Joined: May 6th, 2008, 22:53
Posts: 2138
Location: England
@Aariyan,

I agree with Doomer. Here are a few more comments...

Aariyan wrote:
AHCI is defined as "a data movement engine between Memory and SATA devices".

No it isn't. :) You don't explain the source of this (misinformed) definition, but I suggest you read some more about AHCI, and read (at least some) of the specification itself:
http://www.intel.com/technology/serialata/ahci.htm
http://download.intel.com/technology/se ... rev1_3.pdf
A useful starting point for you, would be section 1.7 "Theory of Operation" in the AHCI spec v1.3 that I linked above.

Aariyan wrote:
So, Is AHCI is enhanced version of DMA?

No.

Aariyan wrote:
Can anybody give me more clarification on this?

As an example: For part of its operation, an AHCI HBA uses DMA to access data in system memory, acting as a PCI bus master. However, as you will read in the specification, the AHCI specification defines much more than this.


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