Origin of "partition" in storage devices

Paul Berger phb.hfx at gmail.com
Mon Jan 31 17:28:08 CST 2022

On 2022-01-31 18:21, Fred Cisin via cctalk wrote:
> 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 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

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.


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