Browse Prior Art Database

Data Dependent Execution Time for CVB (Convert to Binary)

IP.com Disclosure Number: IPCOM000103167D
Original Publication Date: 1990-Jul-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 44K

Publishing Venue

IBM

Related People

Le, HQ: AUTHOR [+2]

Abstract

Disclosed is a system that decreases the execution timer of multicycle instructions, depending on the data presented to the execution element.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 74% of the total text.

Data Dependent Execution Time for CVB (Convert to Binary)

      Disclosed is a system that decreases the execution timer of
multicycle instructions, depending on the data presented to the
execution element.

      Multicycle instructions such as Multiply or Convert to Binary
and others lend themselves to a decrease in execution time, depending
on the data of the operands.  Typically, the execution time of a CVB
(Convert of Binary) can be reduced by examining the high order
decimal digits as they appear in the high order 32 bit word of the
instruction.

      Assuming it has been decided to retire two decimal digits per
execution cycle, then it is possible to examine all four bytes of the
high order 32 bit word and determine how many leading bytes are zero.

      During the first execution cycle of a total of eight execution
cycles for the CVB instruction, the following decision can be made:
If 1 LZB (leading zero byte)  1.  Generate a skip 1 cycle signal.
   2.  Decode and convert byte 1.
If 2 LZB                      1.  Generate a skip 2 cycle signal.
   2.  Decode and convert byte 2.
If 3 LZB                      1.  Generate a skip 3 cycle signal.
   2.  Decode and convert byte 3.
If 4 LZB                      1.  Generate a skip 3 cycle signal.
   2.  Decode and convert byte 4 even though it maybe zero.
                               3.  Set...