I am currently in the process of getting a Toshiba Tecra 730CDT and while I wait for it to arrive have been sourcing drivers for it, now while I was reading the specifications for it, the software list states "MS-DOS 6.22 w/Special Enhancements", which interested me greatly. After a quick search of the net found a download which creates this enhancement disk (sep622.exe), and starting testing on a virtual machine.

So, Toshiba replaces the following Microsoft files with their modified ones:

ANSI.SYS
CGA.GRB
DISPLAY.SYS
EGA.CPI
EGA.GRB
EGA.SYS
EGAMONO.GRB
EMM386.EXE
FDISK.EXE
FORMAT.COM
GRAPHICS.COM
GRAPHICS.PRO
IO.SYS
KEYB.COM
KEYBOARD.SYS
MODE.COM
MONO.GRB
SMARTDRV.EXE
VGA.GRB
VGAMONO.GRB

Now nothing much has changed on a reboot no extra messages on anything like that.

Now, the supplied documentation does not shed much light on what exactly has been enhanced, I can make some assessments such as these are to improve compatibility with Toshiba's proprietary hardware? Such as:

EMM386.EXE is probably coded to know where certain adapter regions are in the upper memory (i.e. Toshiba's own PCMCIA adapter area, etc.) to make it more compatible.

SMARTDRV maybe tweaked to work with the Toshiba disk controller features? I have not done an in-depth compare of the files yet, just a simple play, so SMARTDRV reports it is now version 5.01.T1 instead of just 5.01.

DISPLAY.COM and EGA.CPI are modified to work better with the LCD panel and C&T video card, etc.

The Toshiba versions are actually larger file size apart from SMARTDRV and VGAMONO.GRB (same size).

So, does anyone out there have any information on what is actually enhanced in these files or the features that provide? I am very interested what has been changed in IO.SYS as that is a key file in DOS.