/* INTRO.TXT - Introduction to the KLH10
/* $Id: Intro.txt,v 2.4 2001/11/19 12:11:30 klh Exp $
/* Copyright © 1997,2001 Kenneth L. Harrenstien
** All Rights Reserved.
** This file is part of the KLH10 Distribution. Use, modification, and
** re-distribution is permitted subject to the terms in the file
** named "LICENSE", which contains the full text of the legal notices
** and should always accompany this Distribution.


All KLH10 documentation is online in ASCII text files for
simplicity and portability. The contents, in suggested order of
perusal, are as follows:

Intro.txt - General intro
news.txt - Changes from previous versions
install.txt - Build, install, & configuration instructions
usage.txt - General usage instructions

klt20.txt - KL10 TOPS-20 installation and startup
klt10.txt - KL10 TOPS-10 installation and startup
kst20.txt - KS10 TOPS-20 installation and startup
kst10.txt - KS10 TOPS-10 installation and startup
ksits.txt - KS10 ITS installation and startup

backgrnd.txt - Background comments
coding.txt - Coding guidelines
cmdref.txt - Command reference
cmdsum.txt - Command summary cheat sheet
dfkfb.txt - KL10 timing diagnostic
dvhost.txt - Special host device
history.txt - Historical notes
kldiff.txt - Differences from real KL10
utils.txt - KLH10 Utilities
vtape.txt - Virtual tape details


"KLH10" is an emulator for the PDP-10 series of machines from
Digital Equipment Corporation. The most important thing to know is
that this is a MACHINE emulator. It emulates a specific PDP-10 CPU
and all necessary I/O devices, running a site's existing operating
system (monitor) binary without change -- which then runs user-mode
application programs just as if they were on a real PDP-10. Even
floating-point results are bit-identical.

This means sites must continue to manage the virtual system in
the same way as a real one, without the old hardware. However, the
emulator doesn't monopolize the actual platform, and runs as a set of
simple user processes that co-exist with other software on the native
system. It is possible to configure it so that no actual CPU time is
used while the virtual system is idle.

The KLH10 emulator is extremely portable and flexible -- it is
written in ANSI C so that it can be ported to new platforms quickly,
and new "virtual hardware" can readily be added. The following
describes the currently supported versions:

Emulation Target: KL
CPU: KL10B with extended addressing
Memory: 4MW MF20 (22 bits - 8192 pages of 512 words)
Microcode: v.442 (supports final versions of TOPS-10 or TOPS-20)
Devices available:
DTE - one CTY
RH20 - up to 8 (7 if using a NI20)
Disk - 8 RP06 or RP07 drives per RH20
Tape - 8 TM02/3 formatters per RH20, with one TU45/TU77 each
Network - one NI20 (KLNI/NIA20) ethernet interface

Emulation Target: KS
Memory: 512KW (19 bits - 1024 pages of 512 words)
Microcode: ITS v.262 (supports final version of KS10 ITS)
DEC v.130 (supports final versions of KS TOPS-10/20)
Devices available:
FE - one CTY
RH11 - up to 2
Disk - 8 RP06 or RP07 drives per RH11
Tape - 8 TM02/3 formatters per RH11, with one TU45/TU77 each
Network - one "ACC LH-DH" IMP interface (ITS only)

Supported Host Platforms:
Compaq/DEC Alpha with Tru64 (formerly Digital Unix, formerly OSF/1)
SUN Sparc with Solaris
Any x86 with FreeBSD, NetBSD, or Linux
Plus: Any system providing equivalents to basic Unix system calls.
WNT/W2K ports are possible.

Memory: KL: 35MB (3MB program, 32MB emulated PDP-10 memory)
KS: 6MB (2MB program, 4MB emulated PDP-10 memory)
Disk: .2-.3 GB per RP06, .5-.9 GB per RP07, 50+GB per dynamic RPxx
Tape: optional, can use any variable-record-length drive
Network: optional, LAN interface advised (can share single interface
with native OS, but a second may be desirable)

Varies with job mix and platform architecture, but general
observations suggest the following ratios relative to a
real PDP-10 (where 1.0 = KL10 speed):
SPARC: (MHz / 200)
Alpha: (MHz / 250)
x86: (MHz / 200)
Thus, a 450MHz x86 would provide slightly over 2x KL speed.


The KLH10 internals are organized in a fashion roughly similar
to that of actual hardware. There is a "KN10" process equivalent to a
KS10 or KL10 processor that carries out all CPU operations and is
continuously running, except when the KLH10 user-interface command
parser has control. Most importantly, each hardware device is
implemented as a separate subprocess, with optional direct access to
main PDP-10 memory for data transfers.

This architecture has several advantages:

- It can take advantage of multi-processor host platforms.
- The emulated CPU never needs to wait for I/O. This considerably speeds
up operation, compared to a non-threaded emulator which must
block on disk I/O.
- It can directly use very slow physical devices such as magtape drives
(half-inch, 8mm, 4mm, DLT, etc). Virtual tapes (i.e. tape images
on disk) are also supported.
- The sub-process implementation is more portable and robust than
a threaded implementation.
- Device failures need not be fatal. The NIA20 network device for example
can be reloaded and restarted without stopping the KN10 or the
TOPS monitor.


There are two terms used in the documentation and source that
may cause confusion: KLH10 and KN10.

"KLH10" refers to the entire software product covered by the license.
This is theoretically a proper name ("KLH10 has") but is
often used as an object name ("the KLH10 has").

"KN10" refers to the virtual PDP-10 created at runtime by the
"kn10" executable image. It is specifically intended to
serve as an object name alongside the physical PDP-10s
KA10, KI10, KL10, and KS10.

Nearly all software products are referred to like people (ITS, Emacs,
Oracle, Solaris, etc) and the same can be done with "KLH10". However,
to emphasize that it emulates a hardware device, it is often still
referred to as an object -- "the KLH10". In fact this objectification
urge is so strong that it is actually difficult to avoid using the
articles "the" and "a". The term "KN10" was invented to help maintain
the distinction between the product and the virtual machine/object.

I will let others speculate on why English is this way.