Specifications

Hawk 2XL Product Manual, Rev. B 11
Notes for Sections 4.2.
[1] Execution time measured from receipt of the last Byte of the Command Descriptor Block (CDB) to the
request for a Status Byte Transfer to the Initiator (excluding connect/disconnect).
[2] Maximum times are specified over the worst case conditions of temperature, voltage margins and drive
orientation. When comparing specified access times, care should be taken to distinguish between typical
access times and maximum access times. The best comparison is obtained by system benchmark tests
conducted under identical conditions. Maximum times do not include error recovery.
[3] Typical Access times are measured under nominal conditions of temperature, voltage, and horizontal ori-
entation as measured on a representative sample of drives.
[4] Assumes no errors and no sector has been relocated.
[5] Rate measured from the start of the first sector transfer to or from the Host.
[6] Assumes system ability to support the rate given and no cable loss.
[7] Simulated.
4.3 Start/stop time
After DC power has been applied, the drive becomes ready within 20 seconds if the Motor Start Option is dis-
abled (i.e. the motor starts as soon as the power has been applied). During this time the drive responds to
some commands over the SCSI interface in less than 3 seconds. Stop time is 20 seconds from removal of DC
power.
If the Motor Start Option is enabled, the internal controller accepts the commands listed in the SCSI Interface
Product Manual* less than 3 seconds after DC power has been applied. After the Motor Start Command has
been received the drive becomes ready for normal operations within 13 seconds typically. The Motor Start
Command can also be used to command the drive to stop the spindle*.
There is no power control switch on the drive.
4.4 Prefetch/multi-segmented cache control
The drive provides prefetch (read look-ahead) and multi-segmented cache control algorithms that in many
cases can enhance system performance. “Cache” as used herein refers to the drive buffer storage space when
it is used in “cache” operations. To select prefetch and cache features the host sends the Mode Select com-
mand with the proper values in the applicable bytes in Mode Page 08h. Prefetch and cache operation are inde-
pendent features from the standpoint that each is enabled and disabled independently via the Mode Select
command. However, in actual operation the prefetch feature overlaps cache operation somewhat as is noted in
Sections 4.5.1 and 4.5.2.
All default cache and prefetch Mode parameter values (Mode Page 08h) for standard OEM versions of this
drive family are given in Tables 8a and 8b.
4.5 Cache operation
In general, on “N” models 202,448 bytes of the 256 Kbyte physical buffer space, and on “W” and “WC” models,
431,136 Kbytes of the 512 Kbytes of physical buffer space in the drive can be used as storage space for cache
operations. The buffer can be divided into logical segments (Mode Select Page 08h, byte 13) from which data
is read and to which data is written. The drive maintains a table of logical block disk medium addresses of the
data stored in each segment of the buffer. If cache operation is enabled (RCD bit = 0 in Mode Page 08h, byte
2, bit 0. See SCSI Interface Product Manual P/N 77738479), data requested by the host with a Read command
is retrieved from the buffer (if it is there), before any disc access is initiated. If cache operation is not enabled,
the buffer (still segmented with required number of segments) is still used, but only as circular buffer segments
during disc medium read operations (disregarding Prefetch operation for the moment). That is, the drive does
not check in the buffer segments for the requested read data, but goes directly to the medium to retrieve it. The
retrieved data merely passes through some buffer segment on the way to the host. On a cache “miss”, all
datatransfers to the host are in accordance with “buffer-full” ratio rules. On a cache “hit” the drive ignores the
“buffer-full” ratio rules. See explanations associated with Mode page 02h (disconnect/reconnect control) in the
SCSI Interface Product Manual P/N 77738479.
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