[AT]
Expects: AH    17H
AL    transfer rate: 00H = (reserved; don't use)
01H = 360K diskette in 360K drive
02H = 360K diskette in 1.2 MB drive
03H = 1.2 MB diskette in 1.2 MB drive
04H = 720K diskette in 720K drive
DL    diskette drive number: 00H thru 03H
                                                                  
Returns: AH    BIOS disk error code if CF is set to CY
                                                                  
Info: This should be called before a format operation (INT 13H 05H) to
set the controller for the correct drive speed and track-stepping
option.

Notes:   This does NOT support 1.44 MB or 2.88 MB drives.  Use
INT 13H 18H, since it is more flexible.

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INT 13H 17H: Set Media Transfer Rate