(quoting Jack Ellis):
To set the record straight --
1) None of my older UDMA/XDMA/XCDROM drivers support SATA. They
were never designed for it. They also have many never-fixed "bugs".
I have not supported any UDMA/XDMA/XCDROM releases after February 2006.
2) All of the "hacked" GCDROM/XGCDROM/... drivers (all based upon
my 2006 XCDROM) may or may not support SATA and/or IDE drives.
When I last tested XGCDROM on my system, it found no drives of
either SATA or IDE type (mine is an IDE CD/DVD "combo" drive).
Also, all of the "hacked" xxCDROM drivers can handle CD drives
only, maybe including DVD drives too, but I cannot be certain.
As their names imply, they do not handle hard-disk drives.
3) Only UIDE and UIDEJR will detect and support both SATA and IDE
hard-disks and CD/DVD drives, at present and as far as I know.
UIDE also caches A: or B: diskettes but "calls the BIOS" to do
diskette I-O (UIDEJR ignores diskettes). UIDE/UIDEJR can run
AHCI drives on mainboards that have a "legacy" or "native IDE"
setting for AHCI controllers, i.e. the drives can be addressed
using standard SATA/IDE I-O logic.
4) At-least UIDEJR "Is needed!" on SATA systems. GCDROM/XGCDROM
may or may-not handle SATA and IDE CD/DVD drives due to "bugs"
as I noted above. Permitting only the BIOS to run SATA disks
may work in "real mode", e.g. when using only UMBPCI for upper
memory. But, when using "protected mode" (JEMM386/JEMMEX, or
other "EMM" drivers), many BIOS routines that still omit "VDS"
logic must run disks in only "PIO mode", not UltraDMA, as they
are "cheap" or overloaded and so save logic by omitting "VDS".
This destroys hard-disk performance. UIDEJR has its own 128K
XMS buffer to do "misaligned" or otherwise-unsuitable UltraDMA
I-O. It thus restores system speed which a "cheap" BIOS will
otherwise lose!
5) Either UIDE or LBACache is very highly recommended for any DOS
system. DOS directories are still handled with only 512-byte
single sector I-O, that runs terribly slow. Caching only the
directories (as I did in 2006 for QCACHE) greatly improves DOS
speed; also caching data files through either UIDE or LBACache
will hugely increase DOS speed! Some feel current hard-disks
are "fast enough", but I still feel UIDE or LBAcache should be
tested by every user, and then they can decide for themselves!
P.S. The 16-Jun-2010 UIDE driver package available on iBiblio is again
hopelessly obsolete, and the current 15-Aug-2010 UIDE files, from
Johnson Lam's website, should replace the iBiblio files, so users
can have much better "protected mode" performance. Finally, it
might be best to delete all the older UDMA/XDMA/XCDROM/GCDROM/...
drivers, which have uncorrected "bugs" and may or may not support
SATA and IDE together (usually not). Might be less-confusing to
new users, who would not "wonder" so much re: what driver to use.
Johnson and I will continue to support UIDE/UIDEJR.
Best wishes,
Jack R. Ellis
http://johnson.tmfc.net/dos/driver.html
http://www.ibiblio.org/pub/micro/pc-stuff/freedos/files/dos/udma/
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