Merge branch 'next-release'
This commit is contained in:
Jeff Parsons
commit
e498664d32
4 changed files with 64 additions and 7 deletions
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@ -5,7 +5,7 @@ Welcome to PCjs, home of [PCx86](/docs/pcx86/), the original IBM PC simulation t
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one of several JavaScript Machines in the [PCjs Project](https://github.com/jeffpar/pcjs), an open-source project that
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includes:
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* [PCx86](/docs/pcx86/), an x86-based emulator of [IBM PC and PC-compatible](/devices/pcx86/machine/) machines
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* [PCx86](/docs/pcx86/), an x86-based emulator of [IBM PC and PC-compatible Machines](/devices/pcx86/machine/)
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* [PC8080](/modules/pc8080/), an 8080 machine emulator (e.g., [Space Invaders](/devices/pc8080/machine/invaders/) and the [VT100 Terminal](/devices/pc8080/machine/vt100/))
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* [C1Pjs](/docs/c1pjs/), an emulation of the 6502-based [Ohio Scientific Challenger 1P](/devices/c1p/)
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* [PDPjs](/docs/pdpjs/), a set of emulation modules supporting [PDP-10](/devices/pdp10/machine/) and [PDP-11](/devices/pdp11/machine/) machines
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@ -26,7 +26,7 @@ PCx86 has steadily evolved to support more classic x86-based machines, including
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and the 80386-based COMPAQ DeskPro 386. PCx86 fully supports the original machine ROMs, video cards, etc, and all
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machines run at their original speeds.
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The goals of the [PCjs Project](/docs/about/) project are to create fast, full-featured simulations of classic
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The goals of the [PCjs Project](/docs/about/) are to create fast, full-featured simulations of classic
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computer hardware, help people understand how these early machines worked, make it easy to experiment with different
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machine configurations, and provide a platform for running and analyzing old computer software.
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58
_posts/2017-02-28-learning-the-pdp-10.md
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58
_posts/2017-02-28-learning-the-pdp-10.md
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@ -0,0 +1,58 @@
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---
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layout: post
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title: Learning the PDP-10
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date: 2017-02-28 22:00:00
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permalink: /blog/2017/02/28/
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---
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Since I've more or less achieved all my goals for the PCjs [PDP-11 Emulator](/devices/pdp11/machine/), I've decided
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to turn my attention to an even older historically important DEC computer: the [PDP-10](https://en.wikipedia.org/wiki/PDP-10#Cancellation_and_influence).
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Having never used a real DEC PDP-10, I've had a steep learning curve creating a [PDP-10 Emulator](/modules/pdp10/).
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So far, the only [PDP-10 Hardware Documentation](/pubs/dec/pdp10/) I've read (or rather, skimmed) is the
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[PDP-10 System Reference Manual (1968)](http://archive.pcjs.org/pubs/dec/pdp10/ka10/DEC-10-HGAA-D_PDP-10_System_Reference_Manual_May1968.pdf).
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To make the process a little less painful, most of my initial development efforts have centered on the built-in PDP-10
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Debugger. In addition to the usual disassembler capabilities, I've also included an assembler, so that I can easily enter
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instruction sequences like this:
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a 100;
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hrli 1,111111;
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hrri 1,444444;
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hlr 2,1;
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hrl 2,1;
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end
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and immediately see the corresponding opcodes:
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>> u 100 l4
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000100: 505040 111111 HRLI 1,111111
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000101: 541040 444444 HRRI 1,444444
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000102: 544100 000001 HLR 2,1
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000103: 504100 000001 HRL 2,1
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It's not a full-featured assembler; it's little more than a brute-force reverse look-up through the disassembler's
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opcode-to-mnemonic tables. But it gets the job done.
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Next, I've written an initial set of [PDP-10 Opcode Tests](/apps/pdp10/tests/) and compared the results to those produced
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by [SIMH](https://github.com/simh/simh), and so far, so good. More than anything else, that's just a testament to DEC's
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excellent documentation.
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One of the challenges in creating a JavaScript-based [PDP-10 Emulator](/modules/pdp10/) involves 36-bit arithmetic, because
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JavaScript bit-wise operators maintain only 32 bits. Extreme care must be taken to use only *arithmetic* operators whenever
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accessing and/or preserving the 4 most-significant bits in any 36-bit value.
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So, before I started this project, I wrote a proof-of-concept [Int36 Class](/modules/shared/lib/int36.js) that supports 36-bit
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addition, subtraction, multiplication, and division, as well as a number of helper functions (e.g., *toString()*). Further
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adaptation will be required, however, because **Int36** multiplication produces 72-bit results and **Int36** division uses 72-bit
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dividends, whereas the PDP-10 uses "double length fixed point" values that contain only 70 bits of magnitude with two matching
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sign bits.
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I just finished writing opcode handlers for all the PDP-10 "Half Word" instructions (i.e., *HLL*, *HRL*, *HRR*, *HLR*, with all
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mode variations and bit extension options), but that's just the tip of the iceberg. Hopefully within another month or
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so I'll be able to find the time to finish the rest of the PDP-10 opcode handlers.
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And then maybe we'll be able to run some *real* PDP-10 software in our browsers.
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*[@jeffpar](http://twitter.com/jeffpar)*
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*Feb 28, 2017*
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@ -149,10 +149,10 @@
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"./modules/shared/lib/reportapi.js",
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"./modules/shared/lib/userapi.js",
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"./modules/shared/lib/keys.js",
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"./modules/shared/lib/component.js",
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"./modules/shared/lib/strlib.js",
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"./modules/shared/lib/usrlib.js",
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"./modules/shared/lib/weblib.js",
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"./modules/shared/lib/component.js",
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"./modules/pc8080/lib/defines.js",
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"./modules/pc8080/lib/cpudef.js",
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"./modules/pc8080/lib/messages.js",
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@ -176,16 +176,15 @@
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],
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"pdp10Files": [
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"./modules/shared/lib/defines.js",
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"./modules/shared/lib/diskapi.js",
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"./modules/shared/lib/dumpapi.js",
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"./modules/shared/lib/reportapi.js",
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"./modules/shared/lib/userapi.js",
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"./modules/shared/lib/int36.js",
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"./modules/shared/lib/keys.js",
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"./modules/shared/lib/component.js",
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"./modules/shared/lib/strlib.js",
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"./modules/shared/lib/usrlib.js",
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"./modules/shared/lib/weblib.js",
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"./modules/shared/lib/component.js",
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"./modules/pdp10/lib/defines.js",
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"./modules/pdp10/lib/messages.js",
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"./modules/pdp10/lib/panel.js",
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@ -211,10 +210,10 @@
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"./modules/shared/lib/reportapi.js",
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"./modules/shared/lib/userapi.js",
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"./modules/shared/lib/keys.js",
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"./modules/shared/lib/component.js",
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"./modules/shared/lib/strlib.js",
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"./modules/shared/lib/usrlib.js",
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"./modules/shared/lib/weblib.js",
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"./modules/shared/lib/component.js",
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"./modules/pdp11/lib/defines.js",
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"./modules/pdp11/lib/messages.js",
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"./modules/pdp11/lib/panel.js",
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@ -5,7 +5,7 @@ permalink: /pubs/dec/pdp10/
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---
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PDP-10 Hardware Publications
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---
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----------------------------
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This page summarizes PDP-10 documentation that was useful in creating [PDPjs](/docs/pdpjs/). In most cases,
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these documents came from the PDF Document Archive at [bitsavers.org](http://bitsavers.org), in the [/pdf/dec/pdp10/](http://bitsavers.org/pdf/dec/pdp10/)
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