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Merge pull request #236 from xexyl/2018-mills

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Landon Curt Noll authored and GitHub committed 2023-03-31 11:33:42 -07:00
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2018/mills/README.md
+165 -164
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@@ -1,7 +1,7 @@
# Best of show # Best of show
Christopher Mills <mrxo@sonic.net> Christopher Mills <mrxo@sonic.net>
Twitter: @MisterXopher Twitter: @MisterXopher
## To build: ## To build:
@@ -21,13 +21,13 @@ make
./prog ./prog
``` ```
At the ">boot" prompt, type return At the `>boot` prompt, type return
At the ":" prompt, type "rk(0,0)rkunix" At the `:` prompt, type `rk(0,0)rkunix`
NOTE: To quit, press Control-E NOTE: To quit, press Control-E.
### Selected Judges Remarks: ### Selected Judges' Remarks:
Do small machines only need small programs? This program weighs in at just Do small machines only need small programs? This program weighs in at just
3636 bytes, which is considerably lighter than the original machine it can replace. 3636 bytes, which is considerably lighter than the original machine it can replace.
@@ -39,7 +39,7 @@ run v0. Just type:
./v0 ./v0
``` ```
NOTE: To quit v0, press Control-E NOTE: To quit v0, press Control-E.
You will be greeted with a familiar prompt of "login". The username and You will be greeted with a familiar prompt of "login". The username and
password are "dmr" and "dmr". To make things more familiar you'll need to password are "dmr" and "dmr". To make things more familiar you'll need to
@@ -49,9 +49,9 @@ create '.' as it hasn't been invented yet on this image!
@ ln dd dmr . @ ln dd dmr .
``` ```
An "ls" will reveal that C hasn't been invented yet! IOBCC anyone? The An `ls` will reveal that C hasn't been invented yet! IOBCC anyone? The
compiler is "bc". It producess assembly, which will then need to be assembled compiler is `bc`. It produces assembly, which will then need to be assembled
together in this order "ops.s bl.s hello.s bi.s" to produce a.out! together like `ops.s bl.s hello.s bi.s` (in that order) to produce a.out!
But wait, we said this was the start of it all! This program can also run a But wait, we said this was the start of it all! This program can also run a
program that replaces an even larger machine that can run BSD 2.9. To start this, program that replaces an even larger machine that can run BSD 2.9. To start this,
@@ -64,10 +64,10 @@ At the ">boot" prompt, type return
At the ":" prompt, type "rk(0,0)rkunix" At the ":" prompt, type "rk(0,0)rkunix"
NOTE: To quit prog, press Control-E NOTE: To quit prog, press Control-E.
This should now be very familiar and it is possible to compile and run one of This should now be very familiar and it is possible to compile and run one of
the very first IOCCC entires "mullender.c" the very first IOCCC entires "mullender.c".
But wait, there is even more! Try: But wait, there is even more! Try:
@@ -75,20 +75,21 @@ But wait, there is even more! Try:
./v6 ./v6
``` ```
At the "@" prompt, type "rkunix" At the "@" prompt, type `rkunix`. You might want to type `stty -lcase` as
otherwise the output will be in all caps.
NOTE: To quit v6, press Control-E NOTE: To quit v6, press Control-E.
## Author's comments: ## Author's comments:
> *This IOCCC entry is dedicated to the late Dennis M. Ritchie* > *This IOCCC entry is dedicated to the late Dennis M. Ritchie*
### The Program ### The Program:
Since this is the 25th "annual" IOCCC, I thought I should mark the occasion Since this is the 25th "annual" IOCCC, I thought I should mark the occasion
with a look back to its earliest roots. At the same time the contest enters with a look back to its earliest roots. At the same time the contest enters
its 34th year of providing a safe forum for poor C code, the C language its 34th year of providing a safe forum for poor C code, the C language
itself is fast approching its 50th anniversary, along with the UNIX operating itself is fast approaching its 50th anniversary, along with the UNIX operating
system whose history is so entwined with. system whose history is so entwined with.
The program delivered here is both a full machine emulation of the original The program delivered here is both a full machine emulation of the original
@@ -96,13 +97,13 @@ PDP-7 that Ken Thompson used to write the first version of UNIX and a full
machine emulation of the PDP-11/40 used by subsequent UNIXes. The `Makefile` machine emulation of the PDP-11/40 used by subsequent UNIXes. The `Makefile`
can build versions that can run each of the following: can build versions that can run each of the following:
1. UNIX v0 for the PDP-7 (circa 1969) 1. UNIX v0 for the PDP-7 (circa 1969)
2. Research UNIX Version 6 (circa 1975) 2. Research UNIX Version 6 (circa 1975)
3. BSD 2.9 (circa 1983) 3. BSD 2.9 (circa 1983)
For reasons to be described in a bit, the last (BSD 2.9) is the default. For reasons to be described in a bit, the last (BSD 2.9) is the default.
### Building and Running BSD 2.9 ### Building and Running BSD 2.9:
To run BSD 2.9, do `make` to build `prog` and then `./prog` to run it. To run BSD 2.9, do `make` to build `prog` and then `./prog` to run it.
@@ -110,13 +111,13 @@ You should see a prompt from the first-stage bootloader that looks like
>boot >boot
Type `RETURN` at this point and you will get to the second-stage boot loader Hit enter/return at this point and you will get to the second-stage boot loader
that looks like that looks like
40Boot 40Boot
: :
The 40 in the prompt indicates that the bootloder has correctly determined The 40 in the prompt indicates that the bootloader has correctly determined
that we are running on a PDP-11/40. that we are running on a PDP-11/40.
At this point, type the rather cryptic command `rk(0,0)rkunix` -- this tells At this point, type the rather cryptic command `rk(0,0)rkunix` -- this tells
@@ -169,7 +170,7 @@ Let's try some:
# df # df
Filesystem Mounted on kbytes used free % used Filesystem Mounted on kbytes used free % used
/dev/rk0 / 1958 1688 270 86% /dev/rk0 / 1958 1688 270 86%
# cc mullender.c # bin/cc mullender.c
# ./a.out # ./a.out
The program you've just run was the [winner of the first IOCCC contest from The program you've just run was the [winner of the first IOCCC contest from
@@ -178,7 +179,7 @@ tightly bound to running on either a PDP-11 or a VAX. Now you have one.
Hitting Control-C will return you to the BSD UNIX prompt. Hitting Control-D Hitting Control-C will return you to the BSD UNIX prompt. Hitting Control-D
will log you out of the single-user session and get you back to the `:login:` will log you out of the single-user session and get you back to the `:login:`
prompt. Here you can log in as `root` and get a full timesharing session. prompt. Here you can log in as `root` and get a full time-sharing session.
Feel free to try things like `vi`. I've taken the liberty of editing the Feel free to try things like `vi`. I've taken the liberty of editing the
`.login` and `.profile` files to set the console to a less traditional setup `.login` and `.profile` files to set the console to a less traditional setup
so that you don't have to wait for the Model 33 KSR teletype to move its so that you don't have to wait for the Model 33 KSR teletype to move its
@@ -193,8 +194,7 @@ possible, but I didn't get around to it... As the Judges can no doubt attest,
Once you've had enough fun in BSD 2.9, type Control-E to exit the emulation. Once you've had enough fun in BSD 2.9, type Control-E to exit the emulation.
Building and Running Research UNIX v6 ### Building and Running Research UNIX v6:
-------------------------------------
Research UNIX v6 and BSD 2.9 use the same executable, but require a different Research UNIX v6 and BSD 2.9 use the same executable, but require a different
disk image. Type `make v6` to build it, then type `./prog` to run it. disk image. Type `make v6` to build it, then type `./prog` to run it.
@@ -248,6 +248,7 @@ Assuming you're more careful than that, we can try a few commands:
{ {
printf("Hello, World!\n"); printf("Hello, World!\n");
} }
^D
# cc foo.c # cc foo.c
# ./a.out # ./a.out
Hello, World! Hello, World!
@@ -255,24 +256,24 @@ Assuming you're more careful than that, we can try a few commands:
Why is Version 6 interesting? Well, it was the oldest version that I could Why is Version 6 interesting? Well, it was the oldest version that I could
find a boot image of that had a C compiler... This C compiler is recognizably find a boot image of that had a C compiler... This C compiler is recognizably
C, but not quite the same syntax as we have today. It's much closer to the C, but not quite the same syntax as we have today. It's much closer to the
[B language] [3] from which it is derrived. In particular, this C compiler [B language] [3] from which it is derived. In particular, this C compiler
would not be able to compile `mullender.c` (as simple as it is), because the would not be able to compile `mullender.c` (as simple as it is), because the
following syntax features don't exist yet: following syntax features don't exist yet:
* The `short` data type doesn't exist yet. Only `int` (`short` will show * The `short` data type doesn't exist yet. Only `int` (`short` will show
up when `long` comes, and the port to the Interdata 7/32 starts to make up when `long` comes, and the port to the Interdata 7/32 starts to make
the idea of portability become important). the idea of portability become important).
* Hexidecimal constants don't exist yet. Digital's computers all used * Hexadecimal constants don't exist yet. Digital's computers all used
octal. octal.
* The array initializer syntax hasn't yet moved to using `=`. It still uses * The array initializer syntax hasn't yet moved to using `=`. It still uses
the older form taken from B, which looks like `array[] { 1, 2, 3 };` the older form taken from B, which looks like `array[] { 1, 2, 3 };`
It can still compile "Hello World!" (note that you must type a Control-D after It can still compile "Hello World!" (note that you must type a Control-D after
you finish entering the code, to let `cat` see an end-of-file). you finish entering the code, to let `cat` see an end-of-file).
This version of UNIX doesn't go into multi-user mode if you do a Control-D. This version of UNIX doesn't go into multi-user mode if you do a Control-D.
Single-user mode was entered because the front-panel console switches were Single-user mode was entered because the front-panel console switches were
set to the magic number 0173030 (this can be changed with a re-compile). set to the magic number 0173030 (this can be changed with a recompile).
Once you are done with Version 6, Type Control-E to exit the simulation. Once you are done with Version 6, Type Control-E to exit the simulation.
@@ -281,20 +282,20 @@ code, and they use the same name for the disk (`rk05.fs`), if you want to go
back to the BSD simulation, you should either delete `rk05.fs` or do a back to the BSD simulation, you should either delete `rk05.fs` or do a
`make clean` before you do a `make`. `make clean` before you do a `make`.
### Building and Running UNIX v0 ### Building and Running UNIX v0:
We now set the Wayback Machine to the very start of it all, 1969. We now set the Wayback Machine to the very start of it all, 1969.
[The story] [4] here is interesting and well worth a read. Bell Labs was [The story] [4] here is interesting and well worth a read. Bell Labs was
pulling out of the Multics project and Ken Thompson and his collegues had pulling out of the Multics project and Ken Thompson and his colleagues had
become accustomed to the relatively nice programming environment. They also become accustomed to the relatively nice programming environment. They also
enjoyed the early computer game [*Space Travel*] [5] and wanted another system enjoyed the early computer game [*Space Travel*] [5] and wanted another system
to run it on. They found a PDP-7 which was already obsolete at the time to to run it on. They found a PDP-7 which was already obsolete at the time to
port *Space Travel* to. The primitive programming environment influenced port *Space Travel* to. The primitive programming environment influenced
Thompson to recreate parts of the Multics experience in the much more Thompson to recreate parts of the Multics experience in the much more
hardware-constrained PDP-7 environemnt. In the summer of 1969, with his wife hardware-constrained PDP-7 environment. In the summer of 1969, with his wife
out on a month-long vacation, Thompson re-wrote a filesystem emulation he had out on a month-long vacation, Thompson rewrote a filesystem emulation he had
been experementing with to include an assembler, a shell, an editor and an been experimenting with to include an assembler, a shell, an editor and an
operating system kernel and hence created the first version of UNIX (although operating system kernel and hence created the first version of UNIX (although
it hadn't been named that yet). it hadn't been named that yet).
@@ -329,10 +330,10 @@ filesystem paths yet*. In other words, we can't say something like
We also haven't invented `.` or `..` yet. In fact, the filesystem isn't even We also haven't invented `.` or `..` yet. In fact, the filesystem isn't even
the traditional UNIX tree structure, it's a directed graph of hard links... the traditional UNIX tree structure, it's a directed graph of hard links...
`ls` needs to be able to read '`.`', the current directory. `dmr`'s home `ls` needs to be able to read `.`, the current directory. `dmr`'s home
directory doesn't have that yet, but we can make it, because the home directory doesn't have that yet, but we can make it, because the home
directory has a hard link to `dd`, which is the directory that holds all directory has a hard link to `dd`, which is the directory that holds all
of the user home directories (this will eventually become ``/``, the root of the user home directories (this will eventually become `/`, the root
path). We can do path). We can do
@ ln dd dmr . @ ln dd dmr .
@@ -384,10 +385,10 @@ Now `ls` will work, and we can try some other things while we are here:
Hello, World! Hello, World!
@ @
The last command is invoking the compiler for an exteremely early version of The last command is invoking the compiler for an extremely early version of
the [B programming language] [3], the predecessor to C. Thompson missed the the [B programming language] [3], the predecessor to C. Thompson missed the
convinience of writing code in a high-level language -- Multics was written convenience of writing code in a high-level language -- Multics was written
a version of PL/1 -- and wanted the same convinience on UNIX. He preferred a version of PL/1 -- and wanted the same convenience on UNIX. He preferred
BCPL (a typeless language) to PL/1. As Dennis Ritchie [wrote] [6]: BCPL (a typeless language) to PL/1. As Dennis Ritchie [wrote] [6]:
> B can be thought of as C without types; more accurately, > B can be thought of as C without types; more accurately,
@@ -407,42 +408,42 @@ on the command line, concatenated together and assembled, producing a single
remained the default name of the binary generated by the linker (and hence remained the default name of the binary generated by the linker (and hence
also by `cc`). also by `cc`).
This system is still has the familiarity of UNIX, with all the two- and This system is still has the familiarity of UNIX, with all the two and
three-letter commands, device files, shell redirection, the same core system three letter commands, device files, shell redirection and the same core system
calls (`read`, `write`, `open`, `close`, `creat`, `fork`, etc.). There are a calls (`read`, `write`, `open`, `close`, `creat`, `fork`, etc.). There are a
number of differences still: number of differences still:
* As noted, there are no file paths * As noted, there are no file paths.
* `read` and `write` do I/O on (18-bit) words. Character I/O to files needs * `read` and `write` do I/O on (18-bit) words. Character I/O on files need
to unpack those to bytes, and of course deal with `NUL` characters. to unpack those bytes, and of course deal with `NUL` characters.
* `exec` was performed by the shell directly. Arguments are passed as * `exec` was performed by the shell directly. Arguments are passed as
four words (eight bytes), and space padded. This matches the format for four words (eight bytes), and space padded. This matches the format for
file names for `open` and `creat`. file names for `open` and `creat`.
* `wait` does not yet exist. A more complicated mechanism for sending and * `wait` does not yet exist. A more complicated mechanism for sending and
recieving messages (`smes` and `rmes`) are used instead. receiving messages (`smes` and `rmes`) are used instead.
* File permission bits are all different, since groups don't exist yet. * File permission bits are all different, since groups don't exist yet.
* User programs are not allowed to run during disk I/O. This is because the * User programs are not allowed to run during disk I/O. This is because the
disk controller's "data break" (DMA) accesses were so fast relative to the disk controller's "data break" (DMA) accesses were so fast relative to the
CPU that transfers would be dropped if an instruction that used CPU that transfers would be dropped if an instruction that used
"deferred" mode (indirection) was executed. This also meant that the "deferred" mode (indirection) was executed. This also meant that the
"program break" (interrupt) routine in the kernel had to specifically "program break" (interrupt) routine in the kernel had to specifically
avoid deferred accesses by using self-modifying code to do indirection avoid deferred accesses by using self-modifying code to do indirection
through pointers. through pointers.
* Although the PDP-7 suppoted a "trap mode" (a primitive supervisor mode), * Although the PDP-7 supported a "trap mode" (a primitive supervisor mode),
the UNIX kernel doesn't use it. This means that user programs could alter the UNIX kernel doesn't use it. This means that user programs could alter
or crash the kernel at will (in fact, there is a system call that returns or crash the kernel at will (in fact, there is a system call that returns
addresses of useful kernel routines so that user code can call them addresses of useful kernel routines so that user code can call them
directly). directly).
As usual, when you are done exploring UNIX v0, type Control-E to exit the As usual, when you are done exploring UNIX v0, type Control-E to exit the
simulator. simulator.
### About the Program ### About the Program:
The program came about when I was looking for something to honor the pending The program came about when I was looking for something to honor the pending
50th anniversary of the C language (because of the mercurial nature of IOCCC 50th anniversary of the C language (because of the mercurial nature of IOCCC
contest scheduling, I chose not to wait for the actual 50th anniversary). contest scheduling, I chose not to wait for the actual 50th anniversary).
I had though of writing self-hosting compilers for a stripped-down version of I had thought of writing self-hosting compilers for a stripped-down version of
C, or maybe even a version of the B language... At the same time, I was C, or maybe even a version of the B language... At the same time, I was
obsessed with the idea of allowing `mullender.c` from 1984 to run. Although obsessed with the idea of allowing `mullender.c` from 1984 to run. Although
that was still a possibility on an interpreted version of B or a stripped-down that was still a possibility on an interpreted version of B or a stripped-down
@@ -457,7 +458,7 @@ Thompson's PDP-7 that allowed them to get the system up and running. Although
source for the entire kernel and about half of the user-space commands were source for the entire kernel and about half of the user-space commands were
present (including the runtime and libraries for the B compiler), the present (including the runtime and libraries for the B compiler), the
remainder needed to be written from scratch, including the shell. The final remainder needed to be written from scratch, including the shell. The final
results of the project are [available on github] [9]. results of the project are [available on GitHub] [9].
None of this was remotely easy (as I was to discover myself). The PDP-7 is None of this was remotely easy (as I was to discover myself). The PDP-7 is
long gone, and the documentation for it is less complete than one would like. long gone, and the documentation for it is less complete than one would like.
@@ -473,43 +474,43 @@ I decided that implementing this PDP-7 would be possible as an IOCCC entry.
The emulator emulates the full machine: The emulator emulates the full machine:
* PDP-7 Central Processor * PDP-7 Central Processor
* Core Memeory Module Type 147 -- extends the core to 8,192 18-bit words * Core Memory Module Type 147 -- extends the core to 8,192 18-bit words
* Extended Arithmetic Element Type 177 -- adds one's-complement * Extended Arithmetic Element Type 177 -- adds one's-complement multiplication,
multiplication, division and shifting division and shifting
* Real Time Clock * Real Time Clock
* Teletype Model 33 KSR * Teletype Model 33 KSR
* Perforated Tape Reader Type 444 * Perforated Tape Reader Type 444
* RB09 Fixed Disk Controller * RB09 Fixed Disk Controller
The [PDP-7] [10] is an odd duck by modern computer standards: The [PDP-7] [10] is an odd duck by modern computer standards:
* 18 bit words, with no byte addressing. * 18 bit words, with no byte addressing.
* Both one's and two's complement math (there is `ADD` for one's complement * Both one's and two's complement math (there is `ADD` for one's complement and
and `TAD` for two's complement). The EAE is entirely one's-complement. `TAD` for two's complement). The EAE is entirely one's-complement.
* "Microcoded" instructions. * "Microcoded" instructions.
* Auto-increment memory locations. * Auto-increment memory locations.
* Non-reentrant function calls (the return address is stored at the indicated * Non-reentrant function calls (the return address is stored at the indicated
address and the PC jumps to the location after it). address and the PC jumps to the location after it).
* The `XCT` instruction, that executes the word loaded from memory as an * The `XCT` instruction, that executes the word loaded from memory as an
instruction. instruction.
* An instruction `LAW` that loads the instruction opcode into the * An instruction `LAW` that loads the instruction opcode into the
accumulator. accumulator.
* Heavy use of "inline" operands. For instance the `MUL` instruction expects * Heavy use of "inline" operands. For instance the `MUL` instruction expects
the second operand to be stored in memory after the instruction. This the second operand to be stored in memory after the instruction. This
pretty much requires the use of self-modifying code. pretty much requires the use of self-modifying code.
* No immediates. Almost all constants have to live in memory locations and * No immediates. Almost all constants have to live in memory locations and
be referenced by address. be referenced by address.
* Common operations, like "subtract" and "inclusive OR" are not directly * Common operations, like "subtract" and "inclusive OR" are not directly
supported on the machine and require multiple instructions and some spare supported on the machine and require multiple instructions and some spare
memory locations to support. Being clever also helps. memory locations to support. Being clever also helps.
* Single accumulator architecture. No direct support for things like stacks. * Single accumulator architecture. No direct support for things like stacks.
* I/O is done with dedicated I/O instructions (which are also microcoded). * I/O is done with dedicated I/O instructions (which are also microcoded).
* The RB09 disk controller gets a special mention here because of its * The RB09 disk controller gets a special mention here because of its
particularly annoying encoding of track and sector offsets in particularly annoying encoding of track and sector offsets in
[packed BCD] [11]. A non-trivial amount of code space in the simulator [packed BCD] [11]. A non-trivial amount of code space in the simulator
is needed to convert into and out of BCD, along with an equivalent amount is needed to convert into and out of BCD, along with an equivalent amount
of code in the UNIX kernel itself. of code in the UNIX kernel itself.
The simulation handles everything I was able to discover about the PDP-7, even The simulation handles everything I was able to discover about the PDP-7, even
things that the UNIX code itself doesn't use. For instance, it correctly things that the UNIX code itself doesn't use. For instance, it correctly
@@ -545,13 +546,13 @@ this problem in two ways:
First, I didn't submit the source code or binary image for v0 UNIX as part of First, I didn't submit the source code or binary image for v0 UNIX as part of
my IOCCC entry. I merely submitted a `Makefile` that can issue a `curl` my IOCCC entry. I merely submitted a `Makefile` that can issue a `curl`
command to fetch a prebuilt v0 disk image from the github repository. I am command to fetch a prebuilt v0 disk image from the github repository. I am
hoping this is considered part of "Legal abose of the rules" which is supposed hoping this is considered part of "Legal abuse of the rules" which is supposed
to be "somewhat encouraged". As per RULE 12, I am justifying said abuse here, to be "somewhat encouraged". As per RULE 12, I am justifying said abuse here,
in the remarks file. in the remarks file.
Secondly, the choice to run the UNIX v0 code is optional. If you are worried Secondly, the choice to run the UNIX v0 code is optional. If you are worried
about Nokia's lawyers running you to ground for running a 50-year old copy about Nokia's lawyers running you to ground for running a 50-year old copy
of a binary image for a machine that is almost completely nonexistant, you of a binary image for a machine that is almost completely non-existent, you
can just not do so. Delete the lines from the `Makefile` and sleep well. can just not do so. Delete the lines from the `Makefile` and sleep well.
You still have two other UNIXes to play with. You still have two other UNIXes to play with.
@@ -571,22 +572,22 @@ So if I have a PDP-7 emulator, how do I run operating systems that expect a
PDP-11? Simple... *I emulate a PDP-11/40 on the PDP-7*. I have written PDP-11? Simple... *I emulate a PDP-11/40 on the PDP-7*. I have written
PDP-7 assembler code to emulate a PDP-11/40 with the following equipment: PDP-7 assembler code to emulate a PDP-11/40 with the following equipment:
* PDP-11/40 (KD11-A) * PDP-11/40 (KD11-A)
* EIS instruction set (KE11-E) * EIS instruction set (KE11-E)
* Memory management unit (KJ11-A) * Memory management unit (KJ11-A)
* Line time clock (KT11-D) * Line time clock (KT11-D)
* 124 Kwords of memory (244 Kbytes) * 124 Kwords of memory (244 Kbytes)
* RK05 fixed disk drive (RK11) * RK05 fixed disk drive (RK11)
* Console TTY (DL11) * Console TTY (DL11)
This required a few tweaks to the emulator. The first problem is that the This required a few tweaks to the emulator. The first problem is that the
RK05 disk is about 2.5 MB, but the RB09 is only about 2 MB. That's easily RK05 disk is about 2.5 MB, but the RB09 is only about 2 MB. That's easily
solveable -- just add more tracks to the RB09. UNIX v0 is unlikely to notice solvable -- just add more tracks to the RB09. UNIX v0 is unlikely to notice
(although the number of tracks is a compile time parameter, and the `v0` (although the number of tracks is a compile time parameter, and the `v0`
build commands set it to the correct value). build commands set it to the correct value).
The second problem is that we are simulating a system that can have up to The second problem is that we are simulating a system that can have up to
124 Kwords of memory on a system with only 8 Kwords total. That meant I needed 124K words of memory on a system with only 8K words total. That meant I needed
to virtualize the PDP-11/40's physical memory (and add a few more tracks to to virtualize the PDP-11/40's physical memory (and add a few more tracks to
the disk to hold the virtualization). the disk to hold the virtualization).
@@ -609,7 +610,7 @@ PDP-11's disk is 16-bit, but the PDP-7's is 18-bit (which the emulator stores
in 32-bit `int`s), a conversion program is needed to unpack the binary disk in 32-bit `int`s), a conversion program is needed to unpack the binary disk
images from 16 bits per word to 32. This in turn needs to be done in the images from 16 bits per word to 32. This in turn needs to be done in the
`Makefile` using standard POSIX tools, which aren't exactly good with binary. `Makefile` using standard POSIX tools, which aren't exactly good with binary.
I had a wierdly clever way to do this with `od`, `awk` and `uudecode` that I had a weirdly clever way to do this with `od`, `awk` and `uudecode` that
I will leave as an exercise for the curious, but I decided it would be easier I will leave as an exercise for the curious, but I decided it would be easier
to do it with the PDP-7 emulator itself, feeding a simple program in on its to do it with the PDP-7 emulator itself, feeding a simple program in on its
boot tape. This required an additional tweak to the emulator, since by default boot tape. This required an additional tweak to the emulator, since by default
@@ -620,8 +621,8 @@ parity). This is also enabled by a compile-time setting (used only for the
Despite the complexity of the PDP-11 instruction set and its emulated I/O Despite the complexity of the PDP-11 instruction set and its emulated I/O
devices and the corresponding primitiveness of the PDP-7's instruction set, devices and the corresponding primitiveness of the PDP-7's instruction set,
the emulation itself is a suprisingly small amount of code, not really taxing the emulation itself is a surprisingly small amount of code, not really taxing
the 8 Kword memory, with about 2.25 Kwords of actual code and a similar the 8K word memory, with about 2.25 Kwords of actual code and a similar
amount of space for the memory virtualization cache and disk block buffer, amount of space for the memory virtualization cache and disk block buffer,
leaving nearly half (3.5 Kwords) of the memory unused. The simulator executes leaving nearly half (3.5 Kwords) of the memory unused. The simulator executes
somewhere around 250 PDP-7 instructions per PDP-11 instruction. On my laptop, somewhere around 250 PDP-7 instructions per PDP-11 instruction. On my laptop,
@@ -638,37 +639,37 @@ window on the dawn of the UNIX era. I feel that someone should complete the
circle here by emulating a VAX 780 on the PDP-11 and run 4.2BSD on it, so that circle here by emulating a VAX 780 on the PDP-11 and run 4.2BSD on it, so that
we can get the [original runtime environment used for the first IOCCC] [13]. we can get the [original runtime environment used for the first IOCCC] [13].
### Compile-time Options ### Compile-time Options:
The following command flags control the compilation: The following command flags control the compilation:
* `-DI="image.fs"`: Name of the disk image file. This must be created * `-DI="image.fs"`: Name of the disk image file. This must be created
offline, and be of the correct size to avoid segmentation violations. offline, and be of the correct size to avoid segmentation violations.
* `-DA=4096`: Setting of the console address switches. This tells the RIM * `-DA=4096`: Setting of the console address switches. This tells the RIM
bootloader where to load the boot image. bootloader where to load the boot image.
* `-DS=0`: Setting of the console data switches. The PDP-7 emulation can * `-DS=0`: Setting of the console data switches. The PDP-7 emulation can
read these with the microcoded `OAS` (OR switches into AC) instruction. read these with the microcoded `OAS` (OR switches into AC) instruction.
By proxy, the PDP-11 emulation can read them via the `CSW` device. By proxy, the PDP-11 emulation can read them via the `CSW` device.
* `-DW=MAP_PRIVATE`: This sets the memory mapping for `mmap`. Setting to * `-DW=MAP_PRIVATE`: This sets the memory mapping for `mmap`. Setting to
`MAP_PRIVATE` makes the disk image be copy-on-write. Setting it to `MAP_PRIVATE` makes the disk image be copy-on-write. Setting it to
`MAP_SHARED` makes the disk image be sharable. Do the latter if you want `MAP_SHARED` makes the disk image be shareable. Do the latter if you want
to preserve the disk contents between sessions. to preserve the disk contents between sessions.
* `-DT=`: List of initializers for the `termios` structure. The v0 UNIX * `-DT=`: List of initializers for the `termios` structure. The v0 UNIX
expects the terminal to be in half-duplex mode, echoing its input, with expects the terminal to be in half-duplex mode, echoing its input, with
swapped CR and NL. The PDP-11 UNIXes don't. swapped CR and NL. The PDP-11 UNIXes don't.
* `-DX=5`: The ASCII code of the control character that causes the simulation * `-DX=5`: The ASCII code of the control character that causes the simulation
to abort. If set to 0, there is no abort code. to abort. If set to 0, there is no abort code.
* `-DY=128`: Controls console I/O parity. If set to zero, the console is * `-DY=128`: Controls console I/O parity. If set to zero, the console is
eight-bit clean. If set to 128, the high bit is set on keyboard reads and eight-bit clean. If set to 128, the high bit is set on keyboard reads and
masked off on printer output ("mark" parity). UNIX v0 expects the latter. masked off on printer output ("mark" parity). UNIX v0 expects the latter.
* `-DV=270`: The size of the disk, in tracks. The UNIX v0 disk has 200 * `-DV=270`: The size of the disk, in tracks. The UNIX v0 disk has 200
tracks (each has 80 sectors of 64 18-bit words). The PDP-11 UNIXes tracks (each has 80 sectors of 64 18-bit words). The PDP-11 UNIXes
increase this to 270, to allow for the larger RK05 disk emulation increase this to 270, to allow for the larger RK05 disk emulation
(406 tracks of twelve 256-word sectors), plus the space for the 124 Kwords (406 tracks of twelve 256-word sectors), plus the space for the 124K words
of virtualized memory and the 8 Kwords of emulator code. of virtualized memory and the 8K words of emulator code.
* `-DP="xxx"`: RIM bootstrap program paper tape image. Be careful with the * `-DP="xxx"`: RIM bootstrap program paper tape image. Be careful with the
quoting here -- there is at least three levels going on. In particular, quoting here -- there is at least three levels going on. In particular,
you will need to escape `$` as `$$` to protect it from `make`. you will need to escape `$` as `$$` to protect it from `make`.
### What is the ASCII art supposed to be? ### What is the ASCII art supposed to be?
@@ -678,23 +679,23 @@ The ASCII art represents a torn piece of [paper tape] [14].
None of this could have been possible without the hard work of None of this could have been possible without the hard work of
* Warren Toomey and the other members of the * Warren Toomey and the other members of the
[The Unix Heratage Society] [15] [The Unix Heritage Society] [15]
* Robert M. Supnik and the other contributors to [SimH] [16], the simulator * Robert M. Supnik and the other contributors to [SimH] [16], the simulator
for historic computer architectures. The number of times I needed to for historic computer architectures. The number of times I needed to
"Use the Source, Luke" on SimH to unravel some dark corner of these "Use the Source, Luke" on SimH to unravel some dark corner of these
machines was uncountable. machines was uncountable.
* [Bitsavers] [17], which acquired, scanned and preserved all the manuals * [Bitsavers] [17], which acquired, scanned and preserved all the manuals
I spent many hours squinting at. I spent many hours squinting at.
* Ken Thompson, Dennis Ritchie, Brian Kernigan, M\. D\. McIlroy, J\. F\. * Ken Thompson, Dennis Ritchie, Brian Kernigan, M\. D\. McIlroy, J\. F\.
Osssanna, Rudd Canaday and the other members of the Bell Labs Osssanna, Rudd Canaday and the other members of the Bell Labs
Computing Science Research Center who were responsible for the invention Computing Science Research Center who were responsible for the invention
of UNIX, the C programming language, and the innumerable other innovations of UNIX, the C programming language, and the innumerable other innovations
that we now take for granted as part of the modern software landscape. that we now take for granted as part of the modern software landscape.
In particular, the [home page of the late Dennis Ritchie] [18] contained In particular, the [home page of the late Dennis Ritchie] [18] contained
a trove of useful information on the evolution of UNIX and C and is a trove of useful information on the evolution of UNIX and C and is
recommended for perusal by others who share my peculiar retrocomputing recommended for perusal by others who share my peculiar retrocomputing
affectations. affectations.
Finally, thanks to my spouse for putting up with the many hours I spent on this Finally, thanks to my spouse for putting up with the many hours I spent on this
nonsense, and treating "I'm working on my IOCCC entry" as an acceptable answer nonsense, and treating "I'm working on my IOCCC entry" as an acceptable answer
faq.md
+5 -2
View File
@@ -50,10 +50,13 @@ Thank you Cody!
See also [Yusuke Endoh](/winners.html#Yusuke_Endoh)'s entry See also [Yusuke Endoh](/winners.html#Yusuke_Endoh)'s entry
[2015/endoh3](/2015/endoh3/README.md) entry which lets one compile it and run [2015/endoh3](/2015/endoh3/README.md) entry which lets one compile it and run
it. it. Another entry that you can enjoy it under is [Christopher
Mill](/winners.html#Christopher_Mills)'s entry
[2018/mills](/2018/mills/README.md) which is a PDP-7 emulator as well as a
PDP-11/40 emulator.
Others are not so easy though we're working on this and over time have added Others are not so easy though we're working on this and over time have added
alternative code and in some cases replaced the original code with code that alternative code. In some cases we replaced the original code with code that
works for modern systems. works for modern systems.