Command Overhead; Mechanical Positioning; Figure 4. Command Overhead; Figure 5. Mechanical Positioning Performance - IBM DTLA-305040 - Deskstar 41.1 GB Hard Drive Specifications

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)

Figure 4. Command overhead

4.4.2 Mechanical positioning

4.4.2.1 Average seek time (without command overhead, including settling)
Command
Type
DTLA-305XXX
Read
Write

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.
Typical (ms)
DTLA-307XXX
9.2 8.2
10.2 9.2
Deskstar 40GV & 75GXP hard disk drive specifications
Time (Typical)
(ms)
0.3
0.1
0.015
0.3
Max (ms)
DTLA-305XXX DTLA-307XXX
10.2
11.2
12
Time (Typical) for
queued command
(ms)
0.3
0.1
0.05
not applicable
9.2
10.2