Determining if a drive supports DMA
The easiest way to
determine if a drive supports DMA or Ultra DMA transfers is to check
the specifications in the manual or on the web site. You can also use
debug
to query the drive directly to determine
what level of DMA, if any, it supports. To do so, boot the PC using a
DOS floppy that contains the debug
utility.
(Running debug
under Windows NT/2000/XP does not
allow you to access the registers needed to perform this test.) At
the DOS prompt, type debug
and press Enter. If the
drive to be tested is connected to the primary ATA interface, type
the following commands at the debug
hyphen prompt,
ending each line by pressing Enter. Note that the first character in
each of the first four lines is the lowercase letter
“o” rather than zero, and that all
“1” characters are the numeral one
rather than the lowercase letter
“l”.
o 1f6 a0 o 1f2 45 o 1f1 03 o 1f7 ef i 1f1
The first line (o 1f6 a0
) specifies the drive to
be tested. The a0
argument specifies the Master
drive. To test the Slave drive, substitute b0
(o 1f6 b0
). The second line (o 1f2
45
) specifies the DMA mode to be tested. Valid arguments
are 40
through 46
, inclusive,
for Ultra DMA Modes 0 through 6, respectively. For DMA
(not Ultra DMA) Modes 1 and 2, use
21
or 22
, respectively. Start
with the fastest mode you believe the drive supports. If the test
fails for this mode, retest using the next- slower mode until you
find a mode that the drive does support. The 03
argument on the third line ...
Get PC Hardware in a Nutshell, 3rd Edition now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.