IBM IC35L036UWDY10 Hard Drive Specifications - Page 108

Mode Disconnect/Reconnect Parameters, Write Buffer Empty Ratio

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8.8.4 Mode Page 2 (Disconnect/Reconnect Parameters) Bit Byte 7 6 5 4 3 2 0 PS RSVD=0 Page Code = 02h 1 Page Length = 0Eh 2 Read Buffer Full Ratio 3 Write Buffer Empty Ratio 4-5 (MSB) Bus Inactivity Limit = 0 6-7 (MSB) Disconnect Time Limit = 0 1 0 (LSB) (LSB) 8-9 (MSB) Connect Time Limit = 0 (LSB) 10-11 (MSB) 12 Maximum Burst Size Fair arbitration DIMM RSVD (LSB) DTDC 13-15 Reserved = 0 Default 82h 0Eh 00h 00h 00h 00h 00h 00h 00h 00h 00h 00h 70h 00h 00h 00h Figure 89. Mode Page 2 (Disconnect/Reconnect Parameters ) The disconnect/reconnect page provides the initiator with the means to tune the performance of the SCSI bus. An initiator may use the IDENTIFY message to grant the drive the general privilege of disconnecting. (Disconnect requests may still be selectively rejected by the initiator by issuing a MESSAGE REJECT). The drive uses the disconnect/reconnect parameters to control reconnection during READ, WRITE, and WRITE AND VERIFY commands. ! Read Buffer Full Ratio is the numerator of a fraction whose denominator is 256. The fraction indicates how full the drive data buffer should be before attempting to reconnect to the SCSI bus. If the ratio is set to 0h, the drive will calculate and use an optimal ratio based on the negotiated transfer rate. ! Write Buffer Empty Ratio is the numerator of a fraction whose denominator is 256. The fraction indicates how empty the drive data buffer should be before attempting to reconnect to the SCSI bus. If the ratio is set to 0h, the drive will calculate and use an optimal ratio based on the negotiated transfer rate. ! Maximum Burst Size is the maximum amount of data that the drive transfers during a data phase before disconnecting if the Initiator has granted the disconnect privilege. This value is expressed in increments of single block size (for example, a value of 0001h means 512 bytes, 0002h means 1024 bytes when the block size is 512 bytes). Disconnections attempted by the drive are on block boundaries only. For the case when (Maximum Burst Size x Block Size) is less than the Block Length, the drive will transfer 1 block of data before attempting to disconnect. Value of 0000h indicates there is no limit on the amount of data transferred per connection. Regardless of the value in Maximum Burst Size the drive disconnects prior to completion of the data phase if the internal data buffer segment becomes empty during a Read command or full during a Write command. Ultrastar 146Z10 hard disk drive specifications 92

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8.8.4 Mode Page 2 (Disconnect/Reconnect Parameters)
00h
00h
00h
Reserved = 0
13-15
70h
DTDC
RSVD
DIMM
Fair arbitration
12
00h
00h
(MSB)
Maximum Burst Size
(LSB)
10-11
00h
00h
(MSB)
Connect Time Limit = 0
(LSB)
8-9
00h
00h
(MSB)
Disconnect Time Limit = 0
(LSB)
6-7
00h
00h
(MSB)
Bus Inactivity Limit = 0
(LSB)
4-5
00h
Write Buffer Empty Ratio
3
00h
Read Buffer Full Ratio
2
0Eh
Page Length = 0Eh
1
82h
Page Code = 02h
RSVD=0
PS
0
0
1
2
3
4
5
6
7
Default
Bit
Byte
Figure 89. Mode Page 2 (Disconnect/Reconnect Parameters )
The disconnect/reconnect page provides the initiator with the means to tune the performance of the SCSI
bus.
An initiator may use the IDENTIFY message to grant the drive the general privilege of disconnecting. (Dis-
connect requests may still be selectively rejected by the initiator by issuing a MESSAGE REJECT).
The drive uses the disconnect/reconnect parameters to control reconnection during READ, WRITE, and
WRITE AND VERIFY commands.
!
Read Buffer Full Ratio
is the numerator of a fraction whose denominator is 256. The fraction indi-
cates how full the drive data buffer should be before attempting to reconnect to the SCSI bus. If the
ratio is set to 0h, the drive will calculate and use an optimal ratio based on the negotiated transfer rate.
!
Write Buffer Empty Ratio
is the numerator of a fraction whose denominator is 256. The fraction
indicates how empty the drive data buffer should be before attempting to reconnect to the SCSI bus. If
the ratio is set to 0h, the drive will calculate and use an optimal ratio based on the negotiated transfer
rate.
!
Maximum Burst Size
is the maximum amount of data that the drive transfers during a data phase
before disconnecting if the Initiator has granted the disconnect privilege. This value is expressed in
increments of single block size (for example, a value of 0001h means 512 bytes, 0002h means 1024
bytes when the block size is 512 bytes). Disconnections attempted by the drive are on block bound-
aries only. For the case when (Maximum Burst Size x Block Size) is less than the Block Length, the
drive will transfer 1 block of data before attempting to disconnect. Value of 0000h indicates there is no
limit on the amount of data transferred per connection. Regardless of the value in Maximum Burst
Size the drive disconnects prior to completion of the data phase if the internal data buffer segment
becomes empty during a Read command or full during a Write command.
Ultrastar 146Z10 hard disk drive specifications
92