INT 41 HARD DISK 0 PARAMETER TABLE ADDRESS

Notes:




The default parameter table array is located at F000h:E401h in 100%

compatible BIOSes; the pointer may be overridden by the hard disk

controller's BIOS to support drive formats unknown to the ROM BIOS.

Not used by some PS/2 models.

BIOSes which support four hard drives may store the parameter tables

for drives 81h-83h immediately following the parameter table pointed

at by INT 41, with a separate copy of the drive 81h table for INT 46.

The check for such an arrangement is to test whether INT 46 points

somewhere other than exactly 16 bytes past INT 41, and the sixteen

bytes starting at offset 10h from INT 41 are identical to the sixteen

bytes pointed at by INT 46.

Another arrangement for BIOSes which support four IDE drives is to have

four tables pointed at by INT 41 in the order primary master,

primary slave, secondary master, and secondary slave, in which case
(for example) a system with only primary master and secondary master

will have valid tables at offsets 00h and 20h, with garbage (but

sectors-per-track = 00h) at offsets 10h and 30h




Format of fixed disk parameters:







Offset  Size    Description     (Table 03196)


00h    WORD    number of cylinders

02h    BYTE    number of heads

03h    WORD    starting reduced write current cylinder (XT only, 0 for others)

05h    WORD    starting write precompensation cylinder number

07h    BYTE    maximum ECC burst length (XT only)

08h    BYTE    control byte (see #03197,#03198)

09h    BYTE    standard timeout (XT only, 0 for others)

0Ah    BYTE    formatting timeout (XT and WD1002 only, 0 for others)

0Bh    BYTE    timeout for checking drive (XT and WD1002 only, 0 for others)

0Ch    WORD    cylinder number of landing zone (AT and later only)

0Eh    BYTE    number of sectors per track (AT and later only)

0Fh    BYTE    reserved

See Also: #00273 - #00277

Bitfields for XT fixed disk control byte:







Bit(s)  Description     (Table 03197)


2-0    drive step speed.

000  3ms.

100  200ms.

101  70ms (default).

110  3ms.

111  3ms

5-3    unused

6      disable ECC retries

7      disable access retries




Bitfields for AT fixed disk control byte:







Bit(s)  Description     (Table 03198)


0      unused

1      reserved (0)  (disable IRQ)

2      reserved (0)  (no reset)

3      set if more than 8 heads

4      always 0

5      set if manufacturer's defect map on max cylinder+1  (AT and later only)

6      disable ECC retries

7      disable access retries