Date: Tue, 14 Apr 1998 12:27:32 +0100 From: Matthias Paul Subject: Re: Harddisk Question To: opendos AT delorie DOT com Reply-to: Matthias DOT Paul AT post DOT rwth-aachen DOT de Message-id: <223ADE13C21@reze-1.rz.rwth-aachen.de> Organization: Rechenzentrum RWTH Aachen Precedence: bulk On Sun, 12 Apr 1998 Paul fULLER asked: > G'day, whats the biggest hard disk that you can run unpartioned with > OpenDOS compared to MS-DOS ? Is it 4.3 gig for both?... The maximum partition size for FAT16 is about 2 GB for both DOSes (because of the 32 KB cluster limitation in MS-DOS). (Maybe, DR-DOS would support 64 KB clusters for up to ca. 4 GB FAT16 partitions, but DOS FDISK does not allow to create such partitions. NT FDISK does, but I've nevr tried what happens if you try to use DR-DOS on such a partition. Doesn't make much sense anyway...) However, the maximum partition size of a DOS drive also depends on your ROM-BIOS support, and peculiarities in INT 13h implementations. (Without special drivers) old ROM-BIOSes do not support hard disks beyond about 530 MB, but this limitation is not imposed by DOS. Some ROM-BIOSe also have problems to access hard disks beyond about 1 Gb (some old SCSI BIOSes), 2,?? Gb, and 4,?? Gb. These limitations are due to the C/H/S remapping (physical & logical geometry), different access methods (logical C/H/S or LBA), and some unsupported combinations of C/H/S under MS-DOS, which BIOSes usually try to avoid for reasons of compatibility. Only very new BIOSes (1997+) support hard disk beyond 8 Gb (the physical limit of the traditional INT 13h interface) using so called 'INT 13h extensions' (which cannot yet be used by any DOS - with the exception of Windows 95 OSR2+). Matthias -------------------------------------------------------------------- Matthias Paul, Ubierstrasse 28, D-50321 Bruehl, GERMANY eMail: Web : http://www.rhrz.uni-bonn.de/~uzs180/mpdokeng.html -------------------------------------------------------------------- Caldera Digital Research Systems/OpenLinux: http://www.caldera.com/ --------------------------------------------------------------------