SUBJECT: Project 7000, Ultra Fast Disks - New Instructions

It is proposed that two new instructions be provided to eliminate 30 ms delaya encountered when a block addreesed has just passed and a full revolution is required before it again is available. These instructions might be called READ AND ROLL and WRITE AND ROLL to imply that memory is addressed so that it seems( to roll in synchronism with the disk. This feature has been proposed forl*8&ldc*These instructions cannot be used simultaneously with the grouping distribution feature. The programmer puts the datsword address ( DWA ) in the control-word address ( CWA 1 part of the control-word and hlpecifiee a word count ( W. C, ) that is a multiple of 2''. When,the disk unit receives the READ AND ROLL inatruction, it begins reading at the beginning of the next block and emits to the high speed part of the exchange the block number ( 0, 21°, 2 x 2'*, 3 x 2'') of the block it is reading. To assure sending each word to the proper location in memory, the exchange adds this emitted number to the CWA and stores the sum as the DWA prior to the processing of the first word.