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Format of diskette parameter table

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Offset Size Description

00h

BYTE

first specify byte
bits 7-4 : step rate
Fh - 2 ms
Eh - 4 ms
Dh - 6 ms
Bh - 8 ms
Ch - 10 ms
Ah - 12 ms
9h - 14 ms
8h - 16 ms
7h - 18 ms
6h - 20 ms
5h - 22 ms
4h - 24 ms
3h - 26 ms
2h - 28 ms
1h - 30 ms
0h - 32 ms
bits 3-0 : head unload time
0Fh = 240 ms

01h

BYTE

second specify byte
bits 7-1 : head load time
01h = 4 ms
bit 0 : non-DMA mode (always 0)
Note : The DOS boot sector sets the head load time to 15ms, however, one should retry the operation on failure.

02h

BYTE

delay until motor turned off (in clock ticks)

03h

BYTE

bytes per sector
00h = 128
01h = 256
02h = 512
03h = 1024

04h

BYTE

sectors per track (maximum if different for different tracks)

05h

BYTE

length of gap between sectors
2Ah for 5.25"
1Bh for 3.5"

06h

BYTE

data length (ignored if bytes-per-sector field nonzero)

07h

BYTE

gap length when formatting
50h for 5.25"
6Ch for 3.5"

08h

BYTE

format filler byte (default F6h)

09h

BYTE

head settle time in milliseconds

0Ah

BYTE

motor start time in 1/8 seconds

---IBM SurePath BIOS---

0Bh

BYTE

maximum track number

0Ch

BYTE

data transfer rate

0Dh

BYTE

drive type in CMOS

See Also:

#03226 at INT 4D/AH=09h