Command: udma2.sys / udma2s.sys
UDMA2.SYS / UDMA2S.SYS are DOS hard-disk caching driver for UltraDMA
UDMA2.SYS / UDMA2S.SYS has to be loaded in CONFIG.SYS / FDCONFIG.SYS.
When FreeDOS is already running, you can load UDMA2.SYS / UDMA2S.SYS
later with DEVLOAD.
UDMA2.SYS / UDMA2S.SYS are out of date. There is NO MORE support
by the author! You should use UIDE.SYS instead.
DEVICE = [path]UDMA2.SYS [/O] [/L] [/S] [...]
DEVICE = [path]UDMA2S.SYS [/L] [/S] [...]
DEVICEHIGH = [path]UDMA2.SYS [/O] [/L] [/S] [...]
DEVICEHIGH = [path]UDMA2S.SYS [/L] [/S] [...]
/O For UDMA2.SYS only, enables output overlap. This REQUIRES an XMS
manager (HIMEMX, etc.) and 128K of XMS memory. If /B is
also specified, or if XMS is not available, overlap will NOT
be enabled, as UDMA2.SYS must then use "DMA only" mode.
/L Limits DMA to "low memory" below 640K. /L is REQUIRED to use
the UMBPCI upper-memory driver, or any similar drivers whose
upper-memory areas do not support DMA. If /L is specified, UDMA2.
SYS or UDMA2S.SYS must reside in LOW memory (as their command-
list is accessed via DMA), or the driver will ABORT loading!
/L causes I/O requests past 640K to go through the driver's XMS
buffer. If /B is specified with /L or if XMS memory is not
available, such I/O is "passed" to the BIOS for execution.
/S For UDMA2.SYS, enables the driver local-stack for "DMA only" mode.
For UDMA2S.SYS, enables the local-stack for all cases. NOTE that
the two drivers handle /S differently! UDMA2S.SYS usually does
not enable a stack (for compatiblity with old versions!) and
requires /S whenever a stack is wanted. UDMA2.SYS always sets
a stack (and ignores /S) for normal or output-overlap usage,
so it requires /S merely for "DMA only" mode. /S is meant
for systems with one or more user programs which set "short"
run-time stacks. /S and /B are independent and both may be
/B Causes XMS memory to be IGNORED, for "backward compatibility".
/B forces UDMA2.SYS or UDMA2S.SYS to use "DMA only" mode. Thus, /B
cancels /O (UDMA2.SYS output overlap is not enabled), causes the
initialization "read tests" in UDMA2.SYS to be omitted, and also
affects /L as noted above.
/Mn Specifies the MAXIMUM UltraDMA "mode" to be used by all disks,
where n is a number between 0 and 7, as follows:
0 = ATA-16, 16 MB/sec. 4 = ATA-66, 66 MB/sec.
1 = ATA-25, 25 MB/sec. 5 = ATA-100, 100 MB/sec.
2 = ATA-33, 33 MB/sec. 6 = ATA-133, 133 MB/sec.
3 = ATA-44, 44 MB/sec. 7 = ATA-166, 166 MB/sec.
Disks designed to a "mode" LESS than the given value will be
limited to their own highest "mode". At present, "mode 7"
ATA-166 is not yet implemented, but any driver CAN handle it
if UltraDMA disks ever use it.
/X For UDMA2.SYS only, disables initialization "read tests". This
switch is a LAST-chance "scheme" of forcing UDMA2.SYS to load on
"problem" systems! Any errors detected by the "read tests"
should be CORRECTED, wherever possible!
For each switch, a dash may replace the slash, and lower-case letters
may be used.
UDMA2.SYS is the most full-featured driver. It offers "output overlap"
which buffers all output and does NOT await output end, so user work
may overlap the DMA! Depending on the user's system and software,
output overlap can yield a significant speed boost. For any output
error or if a 400-msec timer expires, an error message will display.
Output overlap must be enabled with a /O in the CONFIG.SYS line that
loads UDMA2.SYS (see above for switch options).
UDMA2S.SYS is the PREFERRED "small driver", for systems not using out-
put overlap. It omits overlap and initialization "read tests", thus it
achieves an object-file size of 3072 bytes. All other capabilities
of the larger UDMA2.SYS (including an 80386 test) are retained.
UDMA2S.SYS uses the same 640 byte resident "core" as UDMA.SYS or
In CONFIG.SYS / FDCONFIG.SYS:
Copyright (C) 2007 Jack Ellis, updated 2011 by W. Spiegl.
This file is derived from the FreeDOS Spec Command HOWTO.
See the file H2Cpying for copying conditions.