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6.2
Address Translation
When the IDD receives any command which involves access to the disk medium, the IDD
always implements the address translation from the logical address (a host-specified address)
to the physical address (logical to physical address translation).
Following subsections explains the CHS translation mode.
6.2.1
Default parameters
In the logical to physical address translation, the logical cylinder, head, and sector addresses
are translated to the physical cylinder, head, and sector addresses based on the number of
heads and the number of sectors per track which are specified with an INITIALIZE DEVICE
PARAMETERS command. This is called as the current translation mode.
If the number of heads and the number of sectors are not specified with an INITIALIZE DEVICE
PARAMETERS command, the default values listed in Table 6.1 are used. This is called as the
default translation mode. The parameters in Table 6.1 are called BIOS specification.
Number of cylinders
Parameters
Number of head
(logical)
Number of sectors/track
Formatted capacity (MB)
As long as the formatted capacity of the IDD does not exceed the value shown on Table 6.1,
the host can freely specify the number of cylinders, heads, and sectors per track.
Generally, the device recognizes the number of heads and sectors per track with the
INITIALIZE DEVICE PARAMETER command. However, it cannot recognizes the number
of cylinders. In other words, there is no way for the device to recognize a host access area on
logical cylinders. Thus the host should manage cylinder access to the device.
The host can specify a logical address freely within an area where an address can be specified
(within the specified number of cylinders, heads, and sectors per track) in the current
translation mode.
The host can read an addressable parameter information from the device by the IDENTIFY
DEVICE command (Words 54 to 56).
6 - 6
Table 6.1
Default parameters
MPC
MPC
3102AT
3096AT
16,383
16,383
16
8,455.2
8,455.2
C141-E055-02EN
MPC
MPC
MPC
3084AT
3064AT
3043AT
16,383
13,410
8,940
15
63
8,455.2
6,488.2
4,325.5
MPC
3032AT
6,704
3,243.6
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