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Date:      Wed, 11 Apr 2001 12:55:56 +1200
From:      "Juha Saarinen" <juha@saarinen.org>
To:        "Brandon S. Allbery KF8NH" <allbery@ece.cmu.edu>, "Cyrille Lefevre" <clefevre@poboxes.com>
Cc:        <freebsd-stable@FreeBSD.ORG>
Subject:   RE: ATA_ENABLE_ATAPI_DMA gone?
Message-ID:  <KPECIILENDDLPCNIMLOFEEADCBAA.juha@saarinen.org>
In-Reply-To: <250770000.986950121@rushlight.rem.cmu.edu>

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:: Certainly early CDROMs falsely claiming DMA support caused pain in the
:: Linux community until they split off ATAPI DMA support into a separate
:: config option.  One can hope that modern hardware doesn't have that
:: problem, but I have little faith in PC hardware :)

Yes, seen that a lot on various platforms... think lot of it was caused by
"non-standard" AT implementations that differed from vendor to vendor.

Anyway, looked it up. ATA-1 specified these modes:

PIO 0, 1 and 2
DMA 0, 1 and 2 plus multi-word DMA 0.

ATA-2 added the Packet Interface stuff, so that you hang non-hd devices off
the IDE interface, plus block-mode transfers, LBA, more DMA modes etc.

PIO is in fact deprecated, if I read things right.



Cheers,

-- Juha


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