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Browse Prior Art Database

Dynamic Mixed-Endian Mode Control for Input/Output

IP.com Disclosure Number: IPCOM000117779D
Original Publication Date: 1996-Jun-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Beukema, BL: AUTHOR [+2]

Abstract

Disclosed is a means for dynamically selecting endian mode conversions of individual data transfer operations between an Input/Output (I/O) device and system memory.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 73% of the total text.

Dynamic Mixed-Endian Mode Control for Input/Output

      Disclosed is a means for dynamically selecting endian mode
conversions of individual data transfer operations between an
Input/Output (I/O) device and system memory.

      Some computer systems allow the main processor to operate in
either big endian or little endian mode.  The endian mode determines
whether the high oder byte or low order byte of a piece of data is at
the lowest address.  Bridge logic between the main processors memory
(i.e., system memory) and I/O devices may need to treat the data
differently depending on the endian mode the main processor is
operating in and the endian mode of the attached I/O devices.  The
determination of which mode the main processor is operating in is
usually static.  The software has no way of modifying the endian mode
on a dynamic basis; therefore, all software running on the main
processor must then be written for the same endian mode.

      Dynamic determination of endian mode for transfers between I/O
devices and the system memory can be made by using a new endian mode
control bit in an I/O address table or system page table.  In some
computer systems, the bridge logic between the system memory and the
I/O devices must access an I/O address table or a system page table
on each data transfer between memory for two reasons: 1) the address
received from the I/O device is a virtual or 'token' address and
requires translation to access the 'real' page in sys...