To:    John Lohmeyer, Chairman X3T9.2

From:  Dan Davies
       Cipher Data Products

Subj:  MODE SELECT Page 02h, Maximum Burst Size Definition


The current definition of the Maximum Burst Size field (SCSI-2 Rev. 3, page 9-
30) states that the value represents the amount of data that is to be 
transferred between SCSI disconnects.  This wording seems to suggest that the 
field is meaningless if disconnection is not permitted, which was probably not 
the original intent.

The following wording is proposed to allow a more flexible utilization of the 
burst size parameter.

Replace the second paragraph on page 9-30 with the following:

"Maximum burst size field indicates the maximum amount of data that is to be 
transferred before a phase change.  This will normally indicate a disconnect, 
provided disconnect is allowed.  If disconnect is not enabled, the device 
shall send a SAVE DATA POINTER message before continuing the data transfer.  
The value is expressed in increments of 512 bytes.  A value of zero indicates 
no limit on the amount of data transferred.    "

This revised wording provides a benefit to the initiator and the target under 
all circumstances.  The initiator would have a definite point at which an 
ATTENTION condition would be honored during data phases, a feature sorely 
lacking in SCSI.  The target would be allowed to intersperse SAVE DATA POINTER 
messages into long data transfers to avoid long data retransmissions during 
error recovery.