UDMA drivers for DOS (Latest)

Getting old software/games running on older hardware.

UDMA drivers for DOS (Latest)

Postby johnsonlam » 2019-5-15 @ 07:53

It seems that the latest UltraDMA driver or DOS did not made popular in the forum, as I host the driver for over 10 years, I'm quite surprise.

The author Jack R. Ellis did notice some very outdated drivers talking around, the "UDMA 7.0" was seriously outdated and considered unstable.

If you go to <www.vogons.org> and do a search for "XHDD", note that the
two most recent posts refer to the old V7.0 UDMA driver, the last one I
did with Lucho in 2004. V7.0 UDMA is 15 years old and has these items
which are long-since CORRECTED in the current XHDD /B driver:

A) UDMA runs only one "legacy IDE" controller (up to 4 disk drives from
primary-master to secondary-slave). XHDD /B runs up to 14 disks
on up to 5 "legacy" and/or Native-PCI controllers.

B) UDMA does not check all possible PCI-bus "function" codes, only 4 of
the basic ones, so it may NOT find a controller to use. XHDD /B
tests ALL possible PCI-bus "function" codes.

C) UDMA runs only controllers that issue "Data request" before starting
an UltraDMA transfer. XHDD /B normally runs without expecting a
"Data request" but will run such old controllers with a /Q switch.

D) UDMA does NOT switch to its own stack upon entry. XHDD /B does so.

Items (A) and (B) make UDMA "useful" only for very early PC mainboards,
ones that had only the 4 "IDE" ports on 2 80-pin cables. Item (C) may
make UDMA fail on newer controllers that do NOT support "Data request",
like my own VIA VT8237 which is now over 10 years old.

Item (D) is now known to be a DISASTER, since there are some cases when
DOS systems have only about 40 stack bytes, e.g. when COMMAND.COM loads
a new program! Also, issuing VDS or XMS requests needs a minimum 256
stack bytes. UDMA cannot depend on having that much, when it must run
on the user's stack, or when it is "in between" programs!


The latest "Full feature" driver hosted on my personal web server:
http://optimizr.dyndns.org/dos/drivers.html

Please download from my homepage, as it's official and original of all SATA CD-ROM/UltraDMA caching driver!
And I'll forward any question to the author, since he can't visit the forum.

Rgds,
Johnson Lam.
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