JJ "João Jerónimo" wrote:
> Alex Buell wrote:
>>> As someone pointed already, it's pretty likely that MS-DOS 6.22 does
>>> not sup****t LBA routines, so it'll use CHS (which implies a maximum
>>> of 8GB). If the SATA BIOS does not sup****t the virtual mapping I
>>> mentioned above in it's CHS-based routines, then you'll be even more
>>> limited (I think it's the case).
>> That is *exactly* what I've been saying - I even emailed Silicon Images
>> about their BIOS; they might fix it or I might have to patch it myself
>> to put out the right numbers.
> You won't still be able to access past 8GB only with CHS.
Yes INT13 CHS is somehow weird because it truncates/merges the
available hardware op****tunities (28 bits) into three bytes.
16*255*4096 = 1671168 sectors (= 7.96875 GB), not to mention
that ye olde DOS often limit sectors to 63 and add the two gained
bits to the cylinder count, IMHO anyway a useless detour because
the hardware must be fed with recalculated data then.
Older BIOS has even a limit of <2GB and very old HDC can only
access <512 MB with CHS ...
But if you write your own HD-driver, the physical CHS-limit is:
16 heads, 255 sectors, 65536 tracks(cylinders), and this gives
us 267386880 sectors (= 127.5 GB).
So if the the hardware can handle it then it works almost like LBA28
(max= 128 GB), ...except for the unconvenient calculation needs.
__
wolfgang
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