🚀 go-pugleaf

In article: <923681977snz129.os2.7@sunshine.tm>  {R}@sunshine.tm 
(Richard Ashton) writes:
> 
> In article <370e5bb9.13913772@news.demon.co.uk>
>            haeb@pc60.demon.co.uk "Harry Broomhall" writes:
> 
> }   IMHO *don't* use DOS6.2 on such a large drive.  It doesn'r 
support
> } drives over 8Gb correctly.  On drives under this limit the 
largest
> } partition you can create is 2Gb.
> 
> I would like to fully understand this. There are AFAIK three
> "barriers" at 528Mb, 2.1Mb and 8.4Mb.
> 
> 1) 528Mb. This is with old machines that do not have a translating 
BIOS
> where the system bios is limited by the combination of the IDE spec
> and BIOS Int13H capability giving a maximum of 1024 Cyls 16heads 
and
> 63 tracks this equals 512,482,304 bytes or around 504Mb formatted.
> 
> 2a) 2.147Mb. There is BIOS issue with LBA drives that cannot go 
past
>     4097 cyls.
> 
> 2b) 2GB? There is a specific maximum DOS partition size caused by ?
FAT16. Uses a _signed_ integer, to address the allocation units. 
Allows 32768 units, each up to 65536 bytes in size. This gives 2GB. 
In fact NT can use an unsigned integer to give 4GB, but DOS never did 
this (a pity).

> 3) 8.4Gb. DOS 6.xx and earlier also Windows 3.1 cannot see past 
8.4Gb, why?
>           NT4 with SP3 does recognise drives > 8.4Gb
>           Novell 4.11 needs drivers to see past 8.4Gb
>           Novell 5 supports 8.4Gb drives and bigger
>           OS/2 Warp needs a fix to see past 8.4Gb
The 'problem' comes in two parts. There is one, when you reach the 
INT13 IDE limits. DOS, uses INT13 to interface to the drive (this is 
the 'BIOS' interface), before any other 'driver' is loaded. W3.11, 
runs 'on top' of DOS. INT13 as originally defined allows 1023*255*63 
sectors to be addressed, each of 512 bytes. There is a seperate 
'partition' limit, where most of the DOS tools won't allow more than 
four times the single partition size to be allocated. Passing the 
former needs either an OS that loads from the first part of the 
drive, and then handles things itself, or software that understands 
the newer 'extensions' to INT13. Novell 4.11, does the former, N5, 
the latter. NT4 SP3+, modifies it's drivers in the same way.

Best Wishes

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