IBM DTLA-305040 Hard Drive Specifications - Page 24

Command overhead, 4.2 Mechanical positioning

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4.4.1 Command overhead Command overhead is defined as the time required Ÿ from the time the command is written into the command register by a host Ÿ to the assertion of DRQ for the first data byte of a READ command when the requested data is not in the buffer Ÿ excluding - Physical seek time - Latency The table below gives average command overhead. Command type (Drive is in quiescent state) Read (Cache not hit) (from Command Write to Seek Start) Read (Cache hit) (from Command Write to DRQ) Write (from Command Write to DRQ) Seek (from Command Write to Seek Start) Time (Typical) (ms) 0.3 0.1 0.015 0.3 Time (Typical) for queued command (ms) 0.3 0.1 0.05 not applicable Figure 4. Command overhead 4.4.2 Mechanical positioning 4.4.2.1 Average seek time (without command overhead, including settling) Command Type Read Write Typical (ms) DTLA-305XXX DTLA-307XXX 9.2 8.2 10.2 9.2 Max (ms) DTLA-305XXX DTLA-307XXX 10.2 9.2 11.2 10.2 Figure 5. Mechanical positioning performance The terms "Typical" and "Max" are used throughout this specification with the following meanings: Typical. The average of the drive population tested at nominal environmental and voltage conditions. Max. The maximum value measured on any one drive over the full range of the environmental and voltage conditions. (See 7.4 "Environment" on page 0 and 7.5 "DC Power Requirements" on page 0. Deskstar 40GV & 75GXP hard disk drive specifications 12

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4.4.1 Command overhead
Command overhead is defined as the time required
°
from the time the command is written into the command register by a host
°
to the assertion of DRQ for the first data byte of a READ command when the requested data is not in
the buffer
°
excluding
-
Physical seek time
-
Latency
The table below gives average command overhead.
not applicable
0.3
Seek (from Command Write to Seek Start)
0.05
0.015
Write (from Command Write to DRQ)
0.1
0.1
Read (Cache hit) (from Command Write to DRQ)
0.3
0.3
Read (Cache not hit) (from Command Write to Seek Start)
Time (Typical) for
queued command
(ms)
Time (Typical)
(ms)
Command type
(Drive is in quiescent state)
Figure 4. Command overhead
4.4.2 Mechanical positioning
4.4.2.1
Average seek time (without command overhead, including settling)
10.2
11.2
9.2
10.2
Write
9.2
10.2
8.2
9.2
Read
DTLA-307XXX
DTLA-305XXX
DTLA-307XXX
DTLA-305XXX
Max
(ms)
Typical
(ms)
Command
Type
Figure 5. Mechanical positioning performance
The terms “Typical” and “Max” are used throughout this specification with the following meanings:
Typical.
The average of the drive population tested at nominal environmental and voltage con-
ditions.
Max.
The
maximum value measured on any one drive over the full range of the environmental
and voltage conditions. (See 7.4 “Environment” on page 0 and 7.5 “DC Power Requirements” on
page 0.
Deskstar 40GV & 75GXP hard disk drive specifications
12