Browse Prior Art Database

Variable Size for Storage Input/Output Adapter Specification Transport Register Control Blocks

IP.com Disclosure Number: IPCOM000122794D
Original Publication Date: 1998-Jan-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Barnhart, JE: AUTHOR [+3]

Abstract

Disclosed is a method of indicating the size of a control block when the address or pointer to the control block is passed from one processor to another or to an intelligent Input/Output (I/O) device.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 60% of the total text.

Variable Size for Storage Input/Output Adapter Specification Transport
Register Control Blocks

      Disclosed is a method of indicating the size of a control block
when the address or pointer to the control block is passed from one
processor to another or to an intelligent Input/Output (I/O) device.

      It is fairly common for a processor to pass a pointer or the
address in memory of a control block to another processor or to an
intelligent I/O device.  These control blocks normally have some
fixed minimum size that the receiver of the address will then read
from memory.  This invention allows the minimum size of the control
block to  be passed to the receiver along with the address of the
control block.

      This invention uses low-order bits of the address or pointer
being passed to the receiver to encode the length of the control
block to be read by the receiver.  By limiting the alignment of the
control block to be on a power of two bytes, some of the low order
address bits will always be zero.  This allows these bits to be
reassigned as length encode bits.

      For example, if the control block is limited to being aligned
on 4-byte boundaries, the low order two bits of the address being
passed are guaranteed to be zeros and can be reused for length
encode.  This allows a single 32-bit entity to convey both location
and length information to the receiver.

      The low order two bits in this example can be encoded to
signify any length...