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Data Format Conversion: Intel/Non-Intel

IP.com Disclosure Number: IPCOM000100911D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 8 page(s) / 311K

Publishing Venue

IBM

Related People

Bates, M: AUTHOR [+11]

Abstract

This article describes a hardware-format converter, that has been implemented and tested, which allows data of byte, word and dword format, containing program data or pixel values, to be interchanged between Intel, and non-Intel format-processing elements without software data conversion.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 23% of the total text.

Data Format Conversion: Intel/Non-Intel

       This article describes a hardware-format converter, that
has been implemented and tested, which allows data of byte, word and
dword format, containing program data or pixel values, to be
interchanged between Intel, and non-Intel format-processing elements
without software data conversion.

      Systems which comprise an Intel processor (e.g.: iapx80286,
iapx80386) and processors or processing elements developed by other
vendors have the problem of the order of bytes in memory.  Developers
have had to deal with the ordering of bytes in memory of an Intel
DATA FORMAT system being different to that of the majority of other
processor vendors.  This problem has been addressed by previous
products, without success, ending up with software having to do some
(or all) of the format conversion.

      Traditionally the problem has been approached by hardwiring the
bus between Intel (hereinafter I format) and non-Intel (hereinafter
NI format)  processing elements to provide byte-swapping on word data
items.  Other data items, such as byte strings, or since the advent
of the 32-bit iapx80386, doublewords, have had to be format-converted
in software on a per-data-item basis, thus reducing system
performance.  The problem has been compounded by the iapx80386,
because extensions to its architecture allow fast manipulation of
pixels (e.g., BITBLT) if pixels are ordered in reverse.  Details of I
format/NI format data and pixel formats are given in the Appendix.

      The Solution The solution is to provide a hardware format
converter or Image Adapter (IA) between the I and NI format
components of a system.  This converter should allow the transfers of
byte words and dwords between components such that no software
conversion is required and should be capable of reversing the order
of pixels within these data items to cater for pixel data generated
by iapx80386 software.  Such an IA converter should be programmable,
so that format conversion can be dynamically changed, depending on
the data items being transferred, and be bidirectional.

      The remainder of this article describes an implementation.
Important parts are the tables defining the format conversions
required to transfer bytes, words and dwords between processing
elements, without software conversion.  Note that this description
assumes that the IA subsystem is the default, or master format, and
that conversion is to/from I format.  Also, all possible format
conversions are defined by the tables, but only some are discussed in
detail.

      Format Conversion To provide compatibility with the differing
data and pixel map formats between the PC, the IA AP and the IA PI,
with existing PC pixel maps, and with IBM host-generated data, the IA
H/W provides programmer-selectable mechanisms for automatic format
conversion.  The basic assumption in the design is that within the IA
subsystem all data is NI format.  A bidir...