~:-:~~~ RT Personal Computer Technology - Technologists

164 Pages·2009·12.83 MB·English

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~:-:~~~ RT Personal Computer Technology
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Form No. SA23-1057
Foreword Copyright
IBM RT Personal Computer Technology is a A variety of structures and levels of detail ©Copyright International Business Machines
collection of papers by the developers of the may exist in the papers because they were Corporation, 1986. Inquiries related to
RT PC. These papers describe the innovative written as technical articles by different permission to republish an article in full or in
aspects of the RT PC-what we set out to specialists. In order to preserve their part should be directed to the IBM
build, how we built it, and how it works today. authenticity and vitality, the papers have not Corporation, IBM Austin, 854/003, 11400
The papers were written by technical been revised for consistency of style or Burnet Road, Austin, TX 78758.
professionals for readers who are conversant method of presentation. These papers will not
with the vocabulary and concepts of be updated to incorporate future Copies of this book, SA23-1 057, can be
computers and programming. developments. obtained from the local IBM branch office.
IBM employees can order copies from
This book is a one-time statement by the This book is the work of many hands, but Mechanicsburg.
developers for historical and background special acknowledgment is due to Bert Buller
purposes. Although there are several of the Hardware Architecture Group for Cover: An IBM RT Personal Computer Model
overview articles that describe how the coordinating the engineering articles, and to 10 with a larger and somewhat faster
various components work together, the Herb Michaelson, Publications Consultant, for ancestor in the background-an IBM System!
emphasis is on the novel parts of the RT PC shaping both the book and the individuai 370 Model 158 MP.
system. IBM RT Personal Computer articles.
Technology is intended to supply the reader
with an understanding of the things that make Frank Waters, Editor
the RT PC unique, not to provide detailed
descriptions of all of the elements of the
RT PC system.
The papers in this book are not intended to
replace IBM publications in describing the
capabilities of the system components and
how to use them. Keep in mind that the
papers are for general technical
communication purposes; they do not
represent an IBM warranty or commitment to
specific capabilities in the referenced
products.
Preface
Introducing a new architecture to the • a resource manager to provide virtual The development of the RT PC system has
computer marketplace is never done casually. machine, storage, and 1/0 functions and to been a mUlti-location effort. We have
The cost and effort of transition from one ensure data integrity and processing incorporated architectural advances from
architecture to another must be justified by continuity, Yorktown Heights, technology innovations
substantial advantages. It is always tempting from Burlington, graphics peripherals and
to apply advances in technology to improving • a multitasking, multiuser operating system applications from Kingston, and engineering
the performance of existing architectures. that can be tailored to make the RT PC and programming developments from Austin.
Ultimately, however, refinement is subject to suitable for a variety of user requirements, The RT PC has been the work of hundreds of
the law of diminishing returns. Continuing individuals, both within and outside of IBM.
advancement requires fundamental changes. • a coprocessor feature that allows users to The articles in this book describe some of
run programs written for the IBM PC their contributions. I want to convey to
The hardware and software architectures that without interfering with the normal everyone involved my gratitude for their
were originally created for personal operation of the RT PC, efforts and my respect for their
computers had to accommodate the speed accomplishments.
and size constraints of the processors and • and a wide variety of displays, printers,
storage devices that were available at the communications adapters, and processing W. Frank King
time. Techniques that were known to be features, Group Director of Advanced Engineering
effective on mainframes and minicomputers Systems Development
were simply too costly to implement on • in a box that fits on or under a desk. Engineering Systems Products
personal computers. Our intent in designing independent Business Unit
the RT PC has been to use recent With the RT PC, the architectural
technological and architectural advances to sophistication of the personal computer has
avoid the structural limitations of earlier caught up with that of the mainframe.
designs. Perhaps more important, we have laid a
foundation for more efficient exploitation of
The IBM RT PC is a new synthesis of future advances in both hardware and
computer concepts. It combines: software technology. The open-ended ness of
the resource manager and operating system
• A very fast Reduced Instruction Set 32-bit at all levels means that we can easily take
processor for efficient execution of advantage of new applications, devices, and
programs compiled from a higher-level communications techniques.
language,
Ii
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RT Personal Computer Technology ~ : :i~~ IBM Product Design and Development
®
Engineering Systems Products
Contents
IBM RT PC Architecture and Design Decisions G. Glenn Henry 2
Hardware Description P.O. Hester, J.T. Hollaway, and F.T. May 6
Processor Card D.E. Waldecker, K.G. Wilcox, J.R. Barr, 12
W.T. Glover, C.G. Wright, H. Hoffman
System Memory Cards Ronald E. Rowland 18
Floating Point Accelerator Scott M. Smith 21
System Board and I/O Channel for the IBM RT PC Sheldon L. Phelps and John D. Upton 26
System
IBM RT PC Displays and Adapters Joe C. St. Clair 31
Use of Artificial Intelligence to Diagnose Nancy A. Burns and C. Edward Williams 35
Hardware
Manufacturing Innovations to Increase Quality Charles W. Bartlett, A.V. Burghart, 40
and Reduce Cost George M. Yanker
ROMP/MMU Technology Introduction D.E. Waldecker and P.Y. Woon 44
The IBM RT PC ROMP and Memory Management P.O. Hester, Richard O. Simpson, 48
Unit Architecture Albert Chang
ROMP/MMU Implementation D.E. Waldecker, C.G. Wright, 57
M.S. Schmookler, T.G. Whiteside,
R.D. Groves, C.P. Freeman, A. Torres
iii
ROMP/MMU Circuit Technology and Chip Design Raymond A. DuPont, Ed Seewann, 66
Peter McCormick, Charles K. Erdelyi,
Mukesh P. Patel, P.T. Patel
Software Development Tools for ROMP Alan MacKay and Ahmed Chi bib 72
Compiling for the RT PC ROMP M.E. Hopkins 76
Advanced Interactive Executive (AIXTM) Larry Loucks 83
Operating System Structure
Restructuring the AIX User Interface P.J. Kilpatrick and Carolyn Greene 88
Configuration Methods for a Personal Computer Shirley Lerom, Lee Terrell, and Hira Advani 91
System
IBM RT PC AIX Kernel - Modifications and Larry Loucks 96
Extensions
Extendable High-Level AIX User Interface Tom Murphy and Dick Verburg 110
Extended File Management for AIX John M. Bissell 114
The Virtual Resource Manager Thomas G. Lang, Mark S. Greenberg, and 119
Charles H. Sauer
Design of the IBM RT PC Virtual Memory Manager J.C. O'Quin, J.T. O'Quin, Mark D. Rogers, 126
T.A. Smith
The IBM RT PC Subroutine Linkage Convention J.C.O'Quin 131
Implementation of a Virtual Terminal Subsystem D.C. Baker, G.A. Flurry, K.D. Nguyen 134
Use of a Coprocessor for Emulating the PC AT John W. Irwin 137
Coprocessor Software Support Rajan Krishnamurty and Terry Mothersole 142
PC DOS Emulation in the AIX Environment Leonard F. Brissette, Roy A. Clauson, 147
Jack E. Olson
Authors 149
iv
Reader's Guide
The IBM RT Personal Computer Technology Overview Articles Operating System Modifications and
book is divided into four parts. The first Henry 2 Extensions
describes the main hardware elements of the Hester et al. 6 Loucks 83
RT PC system. The second section discusses Waldecker and Woon 44 Loucks 96
the RT PC's 32-bit microprocessor. The third Loucks 83 Bissell 114
section covers the RT PC software and the O'Quin 131
fourth the PC AT coprocessor and AIX's PC Major Hardware Components
DOS emulation functions. Waldecker et al. 12 Virtual Resource Manager
Rowland 18 Lang et al. 119
A reader's guide, for a topical approach to Smith 21 O'Quin et al. 126
this book, is as follows: Phelps and Upton 26 Baker et al. 134
St. Clair 31 Brissette et al. 147
RT PC Microprocessor PC AT Coprocessor
Waldecker and Woon 44 Irwin 137
Hester et al. 48 Krishnamurty and Mothersole 142
Waldecker et al. 57
DuPont et al. 66
User Interface
Kilpatrick and Greene 88
Lerom et al. 91
Murphy and Verburg 110
Brissette et al. 131
1
IBM RT PC Architecture and Design Decisions
G. Glenn Henry
Introduction In addition to these technical objectives, there
Ported Applications / New Applications
The architect of a new system must start by were a number of important practical
making a series of high-level decisions about requirements relative to producing a Application lEt d d 0 r :
D I t x en e pera Ing PC C . ..
e~~ ?pmen I System Functions I ompatlblhty
the hardware and software structure. These successful product: __ .£~h~S_ __ .1. _______ .1 ________
early choices shape all of the ultimate details
of the product. An understanding of the • Easy portability of existing IBM and non- Base Operating System
"reasons why" is important to the person IBM applications
who is trying the understand the resulting VRM
system. In this paper, I will give a very • Easy migration of users and their
general overview of the structure of the RT applications and data from existing systems
Processor and Memory
PC AT Coprocessor
PC and explain the rationale for each of the Management Unit
major decisions that dictated that structure. • The ability to take advantage of I/O
attachments and devices used on other I/O Channel and Devices
Product Objectives systems
The original objective of the project that
Figure 1 Logical Structure of the RT PC
resulted in the RT PC was to build a high- • Straightforward ways for other IBM and
function workstation with capabilities far non-IBM development areas to add and
interfaces that are compatible with other
beyond those of personal computers. modify system functions (Le., an "open"
systems, and IBM-exclusive technology. It is
Specifically required were: system).
this combination of appioaches that allows
the RT PC to meet its sometimes conflicting
• A high-performance 32-bit processor These challenging and, in some cases,
objectives.
conflicting objectives, when combined with
• Large amounts of primary and secondary available technology, shaped the system
storage design as described in the following sections. I/O Channel and Devices
The I/O structure chosen for the RT PC was
• High-function virtual storage capabilities System Structure basically the PC AT 16-bit I/O Channel, with
Figure 1 shows the logical structure resulting some performance improvements. This choice
• High-function APA display devices from the objectives and design systems. makes it possible to use most of the existing
PC AT I/O attachment cards, while providing
• A full-function, multi-tasking operating Figure 2 provides a more detailed look at the acceptable levels of I/O performance with
system structure of the RT PC from a physical native RT PC I/O devices. While providing
viewpoint. As you will see, the specifics of the compatibility with the PC AT, the RT PC I/O
• A high degree of usability system components reflect "something old, channel provides more usable capacity to I/O
something new, something borrowed, and devices, since processor RAM is not
• A flexible, extendable, and open something Blue." The RT PC includes proven connected to the I/O channel and the RT PC
architecture. technologies and functions, innovations,
2
Applications preponderance of code expected to be hardware of the machine. The VRM presents
executed on the RT PC was anticipated to operating systems with a Virtual Machine
Application Development Products
be generated by compilers), Interface (VMI) that not only conceals the
AIX Kernel
complexities of virtual memory management
VRM
• on a single chip for a low-cost, high- and numerous I/O device types, but provides
performance solution, the operating system with a significantly more
Processor MMU
powerful set of functions than are available
System RAM • with an associated MMU chip providing on the bare machine. It is therefore not
advanced virtual storage capabilities, accurate to think of the VRM as a pure
hypervisor, like VM/370. The VMI is, in effect,
• and finally, there was no vendor a higher-level machine to which guest
microprocessor available with the full set of operating systems can be converted. We
PC AT
Disk
Coprocessor these capabilities. considered the VRM necessary because:
The IBM ROMP is a single-chip derivative of • The operating system base that we wanted
Display Other I/O
the 801 processor project of IBM Research to use for the RT PC was not built to run
and thus benefits from the processor on a computer with virtual memory, did not
Figure 2 Physical Structure of the RT PC architecture analysis and advanced compiler provide real-time I/O capabilities, and didn't
architecture design activities associated with provide dynamic install and configuration
I/O Channel Controller includes performance- the 801. In addition, the IBM ROMP has functions. We decided to provide these
assist features such as 32-bit "assembly" special features such as "Load Multiple" and important functions "under" the operating
burst transfer. "Store Multiple" that extend the RISC system, as opposed to making extensive
architecture approach to provide increased modifications to the kernel of the existing
Processor and MMU efficiency and performance in a operating system. For example, the VRM
The most critical choice was obviously that of microprocessor implementation. provides a very fast preemptive interrupt-
the processor and associated Memory based I/O structure, virtual storage
Management Unit (MMU). In spite of the The virtual storage functions provided by the management functions, and dynamic
obvious implications of the objective to ease MMU chip are very powerful. For example, loading and binding of I/O device drivers.
migration of existing applications, we chose a the 32-bit processor address is extended to a This allows, for example, the operating
new processor-the IBM Research/OPD 40-bit virtual address with a high- system kernel to be paged and complex,
Microprocessor (ROMP). performance, hardware-managed "inverted" multi-tasking I/O device drivers to be
page table translation approach. This implemented.
The major reasons for choosing the IBM significantly reduces the size of the page
ROMP were: tables for the large virtual address space • We wanted to achieve a higher degree of
while providing very fast virtual-to-physical program isolation from the hardware details
• It provides a full 32-bit architecture, address translation. Even today, I do not than is possible with the current personal
know of another M M U that provides this level computer operating systems. That is, the
• with high performance (approximately 2 of function and performance. VRM resembles BIOS on the IBM PC, but it
MIPs), provides a much higher level of hardware
Virtual Resource Manager independence. For example, generic device
• using a Reduced Instruction Set Computer When designing the software structure for the classes are supported at the VMI, allowing
(RISC) architecture making it particularly RT PC, we decided to build a Virtual high levels of device transparency and I/O
suitable as a target for compilers (the Resource Manager (VRM) to control the real redirection.
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• We wanted to allow hardware coprocessors functional power to the individual user, system utility functions such as "cp" to
to execute concurrently with ROMP without provides multi-user capabilities where needed, transparently operate on composite data
making major changes to the existing base is open-ended, and has a large user and management objects consisting of an index
and with minimal overhead for resource application base. We concluded that AT&T's file and a data file)
allocation and management (see PC System V suited our purposes better than
Compatibility, below). alternative UNIXes because of the larger • Extensions to exploit use of the powerful
number of applications that had been built to virtual storage support; in particular,
• We needed to isolate the development of run on that base, as well as for a variety of mapped file support which allows an
the RT PC software from changing practical reasons. application to "map" a file into a 256
hardware characteristics during the megabyte virtual address space, and
development process. While this was an In choosing UNIX, however, we accepted the access it with loads and stores, versus
"internal" IBM requirement, the success of need to make significant extensions and reads and writes (a derivative is used by
the VRM in meeting this goal validates its enhancements to meet the needs of our the system to provide mapped text segment
architecture and implementation features expected customers and target applications. support, allowing paging "in place").
relative to providing high levels of hardware This is, of course, the classical trade-off
transparency to the user software. between choosing an existing software • Enhanced signals to allow flexible
system for its pragmatic characteristics exception-condition handling
Consistent with the objectives for a flexible versus developing a new system with
and open system, the VRM provides complete (hopefully) fewer deficiencies but limited • A variety of floating point support functions
facilities for the user to implement and install applications and user familiarity. We chose to
code in the VRM. That is, the detailed start with UNIX and fix the deficiencies while • Simplified installation and configuration
hardware structure is isolated from software retaining upward compatibility for all UNIX processes.
in the preponderance of cases where that is System V interfaces.
desirable, but conversely, all hardware details PC Compatibility
are available to user functions that require Some of the major enhancements made were: In addition to UNIX application portability, our
them. original objective of eaSing user and
• A Usability package to provide easier application migration required a high level of
Operating System and Extensions access to the capabilities of the UNIX compatibility with the IBM PC family. This was
As the base for the RT PC's Advanced command language and to simplify the provided by:
Interactive Executive (AIX1) operating system, implementation of full-screen dialogs
2 3
we chose AT&T's UNIX System V • We • An IBM PC AT hardware coprocessor that
chose UNIX because it provides considerable • Multiple, full-screen virtual terminal support includes an Intel 80286 along with
to permit a single user to run several associated hardware to provide a high level
interactive applications concurrently! time- of PC AT hardware compatibility
1 "Aix" is a trademark of International Business Machines
Corporation. sharing the console display
• An IBM PC DOS "shell" on the AIX
2Trademark of AT&T Bell Laboratories.
• Enhanced console support including Operating System allowing DOS command
extended ANSI 3.64 controls, color support, syntax and semantics to be used to invoke
3The UNIX component of AIX was developed by IBM and
sound support, and mouse support AIX functions
INTERACTIVE Systems Corporation. The UNIX
component is based on INTERACTIVE's IN/ix, which is
based in turn on UNIX System V, as licensed by AT&T • An indexed data management access • IBM PC compatibility modes in the RT PC
Bell Laboratories. (lN/ix is a registered trademark of
method that is integrated into the base BASIC and Pascal compilers, providing IBM
INTERACTIVE Systems Corporation.)
UNIX file system structure (this allows UNIX PC BASIC and Pascal-compatible functions
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• IBM PC diskette access utilities and access • and many base operating system
methods. extensions: message services, shared
segment manager, etc.
One of our key technical decisions relative to
compatibility was to allow the PC AT The Result
coprocessor to execute PC programs We believe the design choices presented here
concurrently with ROMP programs, sharing and the specific designs highlighted in the
system resources such as main storage and following papers allow the IBM RT PC to
the system console. This unique capability is meet its original objectives. Further, these
provided by a combination of the coprocessor directions provide the architectural and design
hardware card and the VRM, which manages base for improvement with minimal disruption
the allocation and sharing of resources in as technology progresses.
such a way that the coprocessor's concurrent
execution is transparent to the operating
system and application programs. For
example, the VRM allocates the console
keyboard to either the coprocessor or the
ROMP and monitors keystrokes for a "hot
key" sequence signalling a need to switch to
the other processor. In a similar fashion,
other system resources are managed so that
the coprocessor applications seem to execute
in a virtual terminal just as the ROMP
applications do.
Application Development Facilities
For the initial release of the RT PC, we
placed a high priority on providing function to
facilitate application development. We
extended the already rich UNIX application
development support functions with:
• a host-compatible SQl data base manager
providing both an API and a full-screen
user interface,
• a FORTRAN compiler, BASIC compiler and
interpreter, and Pascal compiler (in addition
to the C compiler and assembler included in
the base operating system),
• a "net BIOS" set of facilities for access to
the I BM PC Network,
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