Table of Contents
Advertisement
BIOS Disk Definition Tables
The values of BSH and BLM determine (implicitly) the data allocation size BLS,
which is not an entry in the disk parameter block. Given that you have selected a
value for BLS, the values of BSH and BLM are shown in Table 7-4, where all values
are in decimal.
Table 7-4 BSH and BLM Values for Selected BLS
BLS
BSH
BLM
1,024
3
7
2,048
4
15
4,096
5
31
8,192
6
63
16,384
7
127
The value of EXM depends on both the value of BLS and whether the DSM value is
less than 256 or greater than 255, as shown in Table 7-5.
Table 7-5 Maximum EXM Values
BLS
DSM
<
256
DSM
>
255
1,024
°
N/A
2,048
I
°
4,096
3
1
8,192
7
3
16,384
15
7
The value of DSM is the maximum data block number supported by this particular
drive, measured in BLS units. The product BLS x (DSM+I) is the total number of
bytes held by the drive and, of course, must be within the capacity of the physical
disk, not counting the reserved operating system tracks.
The DRM entry is one less than the total number of directory entries, which can take
on a 16-bit value.
The values of ALO and ALl are determined by DRM. The two values ALO and ALl
can together be considered a string of 16-bits, as shown below.
ALO
ALl
15
7-5
Advertisement
Table of Contents
