		  UDMA - the Ultra DMA Driver for DOS
		  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This is a DOS driver, intended to run ONLY a single Ultra DMA hard disk
on south bridges made by Intel, VIA, SiS, ALi, and other manufacturers.
It CANNOT be used with add-on IDE controller cards having on-board BIOS
that already supports Ultra DMA like Promise, SiiG, Adaptec etc.

For optimum and error-free performance, we recommended that you install
your hard disk as a single master drive on the IDE channel, preferably
primary. Coexistence of a slave drive is allowed, but was never tested!
In this case, as the ATA/ATAPI-7 standard says, "Mode shall be selected
no higher than the highest mode supported by the slowest device". So we
don't recommend you connect a slower slave together with a fast master.

For modes higher than 2 (ATA-33), you MUST use 80-conductor IDE cable.
Also consider the following excerpt from the ATA/ATAPI-7 specification:

! The host shall be placed at one end of the cable. It's recommended !
! that for a single device configuration the device be placed at the !
! opposite end of the cable from the host. If a single device	     !
! configuration is implemented with the device not at the end of the !
! cable, a cable stub results that may cause degradation of signals. !
! Single device configurations with the device not at the end of the !
! cable shall not be used with Ultra DMA modes. 		     !

UDMA mode is set to the highest common mode supported by your disk and
chipset. Its value must had been initialised by your BIOS (this doesn't
mean that the BIOS will actually USE it!). The driver handles only read
and write requests to the FIRST PHYSICAL disk. All other requests (seek
etc.) are "passed" back to the BIOS or some other driver for handling.

The disk is assumed to support standard LBA mode (63 sectors, 255 heads
and its "designed" number of cylinders). The driver supports 28-bit LBA
mode (BIOS calls 42h read, 43h write) and handles up to 128 GB disks in
MS-DOS 7.0+, PC-DOS 7.1, ROM-DOS, FreeDOS, newer versions of DR-DOS 7.0
etc. The 24-bit CHS mode (BIOS calls 2 read, 3 write) is also supported
for MS-DOS 6.x and below. CHS mode requires all user files to be on the
first 8 GB of the disk. More data, if present, must be in other disk
partitions and accessed via other operating system supporting LBA mode.

In case the user I/O buffer is not DWORD-aligned, fails a VDS "lock" or
crosses a 64 KB boundary, a request shall be processed through a 64 KB
XMS buffer, using Ultra DMA I/O to and from the buffer. (Not crossing a
64 KB DMA boundary is required by the Bus Master IDE specification, and
DWORD alignment - by the Intel south bridges.) Only requests for over
64 KB of data (non-EDD-compliant!) are "passed" back to the BIOS.

Load the driver in the CONFIG.SYS after the memory managers but BEFORE
the disk caching program, like this: DEVICE[HIGH]=[path]UDMA.SYS

Spread & enjoy!
Jack & Luchezar
