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From: vsnyder@jato.jpl.nasa.gov (Van Snyder)
Newsgroups: comp.sys.atari.st,comp.sys.atari.st.tech
Subject: Re: Setting Floppy Seek Rate in all TOS versions
Keywords: seekrate steprate
Message-ID: <1991Mar19.044454.24718@jato.jpl.nasa.gov>
Date: 19 Mar 91 04:44:54 GMT
Reply-To: vsnyder@jato.Jpl.Nasa.Gov (Van Snyder)
Organization: Jet Propulsion Laboratory, Pasadena, CA
Lines: 42

Here's the poop on setting the seek step rate for floppies, from page 60
of the Rainbow TOS distribution:

"Floprate:      -  Floprate, XBIOS function 41, checks or sets the seek
                   rate for a floppy drive.  This is new; the seek rate
                   must be set with (previously) undocumented variables
                   on earlier versions of TOS.

                   Floprate example.

        int devno, newrate;
        oldrate = Floprate(devno,newrate);

                   This returns the current seek rate if newrate is -1,
                   otherwise sets the seek rate to newrate.  For doing this
                   with previous versions of TOS, the seekrate byte
                   locations for drive A and B are:

                   OS Version   Drive A   Drive B
                   ----------   -------   -------
                    0x0100       $A09      $A0D
                    0x0102       $A4F      $A53

                   In either case valid seek rate byte values are:

                   Value        Rate
                   -----        ----
                   00           6 ms
                   01          12 ms
                   02           2 ms
                   03           3 ms

                   This call does not range check the drive ID or new seek
                   rate.  If devno is zero, it assumes drive A:, if
                   nonzero, drive B:."  That's 41 decimal.
You can get the TOS version from offset 02.w from the place pointed at
by 0x4F2.L (_sysbase).

-- 
vsnyder@jato.Jpl.Nasa.Gov
ames!elroy!jato!vsnyder
vsnyder@jato.uucp