🚀 go-pugleaf

In <9057@pbhyf.PacBell.COM> jcwasik@PacBell.COM (Joe Wasik) writes:

>In article esaholm@polaris.utu.fi (Esa Holmberg) writes:
>>
>>	With DOS 4 (and prior), I have to use Disk Manager to get full
>>	use of my hard disc, as it has more cylinders than DOS 4 can
>>	understand. Has the 1024 cylinder limit finally been removed,
>>	or do I still have to stick with Disk Manager.. ?-)
>>
>DOS 5 allows large disks -- but that increased capacity must still
>remain with the first 1024 cylinders.  I believe this is a problem
>with the BIOS, i.e. it's on a chip.

This is a problem "with the BIOS", but it cannot be overcome easily. Some
low level routines (INT 13H, Funtion 7 or 8, for instance) make use of
the disk parameter set. The maximum value of cylinders to be entered there is
1024. INT 13, function 7, (BIOS low level formatter) as another example
uses the 16 bit CX register for passing the cylinder number and sector 
number (divided into 10 bit cylinder and 6 bit sector, so you may have
64 sectors/track, in theory). Other functions 
and especially programs using these BIOS functions (e.g. the DOS itself)
rely on these and similiar restrictions.
I think DM and dmdrvr.bin intercept the BIOS INT 13 and retranslate an odd
cylinder number into the 1024/64 address space and are this way able to
overcome the problem.

>-- 
>Joe Wasik, Pac*Bell, 2600 Camino Ramon, Rm 4E750V, San Ramon, CA (415)823-2422
>email: jcwasik@clib.PacBell.COM or [...]!pacbell!clib!jcwasik
>If Webster was so smart, how come his dictionaries don't have an index?

Holger

--
|  |   / Holger Veit             | INTERNET: veit@du9ds3.uni-duisburg.de
|__|  /  University of Duisburg  | BITNET: veit%du9ds3.uni-duisburg.de@UNIDO
|  | /   Fac. of Electr. Eng.    | UUCP:   ...!uunet!unido!unidui!hl351ge
|  |/    Dept. f. Dataprocessing |