Date   : Mon, 13 Jun 2005 16:40:47 +0200
From   : John Kortink <kortink@...>
Subject: Re: BBC IDE Drive compatibility list

On 13 Jun 2005 12:45:43 +0100, Jonathan Graham Harston wrote:

>> Message-ID: <050607015502@...>
> 
>jgh@... (Jonathan Graham Harston) wrote:
>> Full information returned by IDE_Identify:
>>   http://mdfs.net/Info/Comp/BBC/IDE/DriveData
> 
>> Some drives tested don't give "sensible" results, and their format
>> capacity has been calculated by doing trail seeks for the end of
>> the disk.
> 
>I've worked out that those drives that don't give "sensible" drive
>sizes are actually returning the drive sizes with some of the
>bytes reversed!
> 
>Drives should return the "disk size" as, for example:
> 
>  &38hi &38lo &37hi &37lo
>   &00   &02   &84   &00  -- &00028400 -- 40M
> 
>But some return it as, for example:
> 
>  &38hi &38lo &37hi &37lo
>   &00   &00   &84   &02  -- &00008402 -- 8M
> 
>IDEDump now checks for this. If &38lo is zero, it swaps &38lo and
>&37lo to get the correct figure.

Be careful drawing conclusions. There have been
major changes in what the Identify command returns
since revision 6 (early 2002) of the ATA standard.

Also, older revisions did not understand LBA, and
have no LBA fields. In later revisions they were
flagged (which was pretty much what was done all
the time : declare what was once mandatory 0 a
flag, and if 1, the new field is present.

A pretty mess, but just taking some random guesses
at to what's going on instead is not the way to go.

Revisions 1 through 6 are all downloadable somewhere
(though only in working draft form, the final drafts
cannot be obtained for free).


John Kortink

-- 

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