31 Jan
2022
31 Jan
'22
3:28 p.m.
On 2022-01-31 18:21, Fred Cisin via cctalk wrote:
On Mon, 31 Jan 2022, Noel Chiappa via cctalk wrote:
The other thing you could do is alter the hard disk bios to support the
disk you wanted to use, many years ago I did that for a gentleman that
had a few 42GB disks, and he gave me one of the drives for my efforts.?
I also recall patching AT BIOS to support drive that didn't match the
geometry of drives in the drive table.
Paul.
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 partitions.
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.
FDISK.COM, 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 floppy)
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