On Mon, 29 Jul 2024, Warner Losh wrote:
The DEC Rainbow had initially a 2.01 and later 2.05 version.
Yes, some OEM licensers made significant changes, particularly when
PC-DOS and "vanilla" MS-DOS didn't handle their disk formats.
And many companies started to use 3.5" drives or 80 track DD 5.25"
drives before DOS 3.30, which was the first official support. So, you
may see various version 2.11 with "720K" drive support.
Including the IBM PC-JX
Later, there was 3.10 (from Ford, semi-bootleg) and then 3.10a and 3.10b
(from suitable
Letters appended were often modifications made by the OEM.
For example, Gavilan used MS-DOS version 2.11, but had their own format.
It wasn't until revision J, K, or L that they supported the "ordinary"
"720K" format.
Note that although the Gavilan came with either a 3.0" drive, or a 3.5"
single sided drive, it supported 3.5" double sided. so, you could replace
the drive with a double sided 3.5". Their drive bezel was proprietary, but
some brands would fit without bezel, and the bezel form Gavilan's Shugart
SA300 drive would fit Shugart SA350.
