Messages in this thread | | | Date | Wed, 12 May 1999 02:40:59 +0200 (MET DST) | From | (Guest section DW) | Subject | RE: The WHY's (RE: ide drive w/dma ... system crash) |
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From goemon@sasami.anime.net Wed May 12 02:17:50 1999
On Wed, 12 May 1999, Guest section DW wrote: > Oh really? So the fact BIOS returns 16383,16,63 instead of 19650,16,63 is > not a BIOS bug? > No, it is the ATA standard.
Another BIOS returns 33483/16/63. Is this part of the standard too? When does it return 16383/16/63 and when does it return larger Cylinders?
Which BIOS returns 33483/16/63 for a disk that has 19650*16*63 = 19807200 sectors?
Below a fragment of the ATA-5 draft standard that I happen to have nearby.
====================================================================== 6.2.1 Definitions and value ranges of IDENTIFY DEVICE words (see 8.12) 1) Word 1 shall contain the number of user-addressable logical cylinders in the default CHS translation. If the content of words (61:60) is less than 16,514,064 then the content of word 1 shall be greater than or equal to one and less than or equal to 65,535. If the content of words (61:60) is greater than or equal to 16,514,064 then the content of word 1 shall be equal to 16,383. 2) Word 3 shall contain the number of user-addressable logical heads in the default CHS translation. The content of word 3 shall be greater than or equal to one and less than or equal to 16. For compatibility with some BIOSs, the content of word 3 may be equal to 15 if the content of word 1 is greater than 8192. 3) Word 6 shall contain the number of user-addressable logical sectors in the default CHS translation. The content of word 6 shall be greater than or equal to one and less than or equal to 63. 4) [(The content of word 1) * (the content of word 3) * (the content of word 6)] shall be less than or equal to 16,514,064. ======================================================================
Very rough translation: large drives shall not reveal that they are large by their geometry parameters. If the number of sectors is at least 16383*16*63 then the disk must report C=16383. Usually the report will be 16383/16/63 but one also finds other values, especially 16383/15/63.
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