On Mon, 31 Jan 2022, Noel Chiappa via cctalk wrote:
Partitions may have appeared in DOS/Windows for much
the same reason; with 32
KB clusters, FAT16 filesystems were limited to 2GB. I distinctly recall
having to use partitions when I bought a 13GB hard drive for my Windows 95
machine (FAT32 only came in with Windows 95 OSR2).
PC-DOS/MS-DOS early partitioning
When PC-DOS/MS-DOS started to support hard drives (XT/5160, March 8,1983),
with PC/MS-DOS 2.00, the limit was 32MB. NOT 2GB.
That limit called for breaking up drives as small as 40MB into multiple
That limit lasted until MS-DOS 3.31 / PC-DOS 4.00 After that, the limit
was bumped up to 2GB. (Probably would have been 4GB if they had used an
UNSIGNED 32 bit number, and given up the option of having negative file
and drive sizes)
The XT/5160 shipped with a 10MB drive, but some people even split that up.
("we're going to share the drive between all of us, so there will be a
partition for DOS and programs, and each person will get a personal
partition for your data."
The XT/5160 used a rebranded Xebec hard disk controller, that included
support for 2 drives, of 5?, 10, 16, and 26MB. It was set for
10MB, but the other sizes could be accessed by adding jumpers to solder
pads on the board. Other sizes could be done with software kludges.
, for partitioning, was included in PC-DOS 2.00 .
The 5160 shipped with the hard disk already formatted.
However low level format, to redo it, or for a third party drive, required
"Advanced Diagnostics", or third party solutions.
"Advanced Diagnostics" was part of the "Hardware Maintenance And
Service" and was on a 160K floppy AND on a cassette! (for machines without
The regular "Diagnostics" that shipped with the machine (both 5150 and
5160) did NOT have hard disk low level format.
Third party controllers usually came with a low-level format utility, or
provision in the hard disk controller's ROM at C800h
Grumpy Ol' Fred cisin at xenosoft.com