neese@adaptex.UUCP (07/23/89)
Okay, its been requested enough. Here is the mode page for the CDC Wren IV and > drives, that is used for disabling/enabling the read ahead buffer. Mode Sense Command: Bits 7 6 5 4 3 2 1 0 Byte 0 0 0 0 1 1 0 0 1 1Ah 1 < LUN > 0 0 0 0 0 2 < PCF > < PAGE CODE > 3 0 0 0 0 0 0 0 0 4 < ALLOCATION LENGTH > 5 0 0 0 0 0 0 0 0 LUN = Logical Unit Number. Almost always zero. PAGE CODE = For this page is 38H ALLOCATION LENGTH = For this page is 28 bytes. Mode Select Command: Bits 7 6 5 4 3 2 1 0 Byte 0 0 0 0 1 0 1 0 1 15h 1 < LUN > <PF> 0 0 0 <SMP> 2 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 4 < PARAMTER LIST LENGTH > 5 0 0 0 0 0 0 0 0 LUN = Logical Unit Number of the SCSI drive. Usually zero, not to be confused with the target ID. PF = Page Format bit. Always set to one. SMP = When set to one, causes the drive to save the page permanently else the page is saved until the next SCSI reset or power down. The PARAMETER LIST is made up of 4 byte header and 8 bytes of media information. These bytes are gotten via a mode sense command. The bytes followng this information is the actual mode page bytes. Mode Select Page 38H Bits 7 6 5 4 3 2 1 0 Byte 0 <PS> 0 1 1 1 0 0 0 38H PAGE LENGTH 1 0 0 0 0 1 1 1 0 14 2 0 0 0 <CE> 0 0 0 1 3 1 1 1 1 1 1 1 1 4 0 0 1 1 0 1 0 0 5 0 0 0 0 0 0 0 0 6 0 0 0 0 0 0 0 0 7 0 0 0 0 0 0 0 0 8-15 < RESERVED (Must be set to zero) > Byte 14 (starting at zero) is the byte that contains the CE bit. CE = When set (1), the drive will perform read look aheads. When set to zero (default) the drive will not perform read look aheads. Roy Neese Adaptec Central Field Applications Engineer UUCP @ {merch,texbell,killer}!cpe!adaptex!neese