IBM Ultrastar 36LZX, Технические характеристики

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Allocation Length must be set to four or greater. The drive transfers the allocation length or four bytes
of READ BUFFER descriptor, whichever is less. The READ BUFFER descriptor is defined in the figure
below.
(MSB) Buffer Capacity
(LSB)
1
2
3
Offset Boundary 0
0 1 2 3 4 5 6 7
Bit
Byte
Figure 113. Read Buffer Descriptor
The value contained in the Buffer Offset field of subsequent WRITE BUFFER and READ BUFFER com-
mands should be a multiple of two to the power of the offset boundary. The offset boundary is always set
to nine, which indicates Sector Boundaries.
8.16.4 Read Data from Echo Buffer (Mode 1010b)
In this mode the drive transfers data from the echo buffer. The echo buffer will transfer the same data as
when the Write Buffer command was issued with the mode field set to echo buffer.
Write Buffer command with the mode field set to echo buffer should be sent prior to the Read Buffer
command; otherwise the Read Buffer command will be terminated with Check Condition "Illegal
Request".
8.16.5 Echo Buffer Descriptor (Mode 1011b)
In this mode, a maximum of four bytes of Read Buffer Descriptor information is returned. The drive
returns the descriptor information for the echo buffer. The Buffer Offset field is reserved in this mode
and must be zero. The drive transfers the lesser of the allocation length or four bytes of following Echo
Buffer Descriptor.
Buffer Capacity (LSB) 3
(MSB) Buffer Capacity Reserved = 0 2
Reserved = 0 1
EBOS=
0
Reserved = 0 0
0 1 2 3 4 5 6 7
Bit
Byte
Figure 114. Echo Buffer Descriptor
EBOS (Echo Buffer Overwritten Supported) bit of zero indicates that the echo buffer is shared by all
initiators.
Buffer Capacity field returns the size of the echo buffer in byte aligned to a four-byte boundary.
Ultrastar 36LZX hard disk drive specifications
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