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Updated PDP-11 READMEs

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Jeff Parsons 2016-10-18 12:03:23 -07:00 • committed by Jeff Parsons
commit fbb36c1d1b
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apps/pdp11/boot/bootstrap/README.md
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@ -1,11 +1,11 @@
---
layout: page
title: PDP-11 Bootstrap Loader
title: DEC PDP-11 Bootstrap Loader
permalink: /apps/pdp11/boot/bootstrap/
---
PDP-11 Bootstrap Loader
-----------------------
DEC PDP-11 Bootstrap Loader
---------------------------
The blog post "[PDP-11 Paper Tape BASIC](http://www.avitech.com.au/ptb/ptb.html)" describes the *Bootstrap Loader*,
a small program used to load the *Absolute Loader*, which in turn loads the *PDP-11 BASIC Paper Tape*.
@ -28,12 +28,13 @@ Here's what the *Bootstrap Loader* looks like:
037774 000765
037776 177550
Using a [PDPjs](/modules/pdpjs/) machine such as the [PDP-11/20 Test Machine with Debugger](/devices/pdp11/machine/1120/test/debugger/),
the *Bootstrap Loader* is easily entered with a single Debugger "edit" command:
Using a [PDPjs](/modules/pdpjs/) machine with the built-in Debugger, such as the
[PDP-11/20 Test Machine with Debugger](/devices/pdp11/machine/1120/test/debugger/), the *Bootstrap Loader*
is easily entered with a single Debugger EDIT ("e") command:
e 037744 016701 000026 012702 000352 005211 105711 100376 116162 000002 037400 005267 177756 000765 177550
You can immediately disassemble the code using `u 037744 040000`:
You can immediately disassemble the code using the Debugger's UNASSEMBLE ("u") command `u 037744 040000`:
037744: 016701 000026 MOV 26(PC),R1 ; @037776
037750: 012702 000352 MOV #352,R2
@ -45,12 +46,38 @@ You can immediately disassemble the code using `u 037744 040000`:
037774: 000765 BR 037750
037776: 177550 .WORD 177550
I also pasted the disassembled code into a listing file, [BOOTSTRAP-16KB.LST](BOOTSTRAP-16KB.lst), and ran [FileDump](/modules/filedump)
to produce a [BOOTSTRAP-16KB.JSON](BOOTSTRAP-16KB.json) that can be pre-loaded into any machine:
filedump --file=BOOTSTRAP-16KB.lst --format=octal --output=BOOTSTRAP-16KB.json
To run the *Bootstrap Loader*, set the PC to 037744 and start the machine:
To run the above code, set the PC to 037744 and start the machine:
r pc=037744
g
Preloading DEC's Bootstrap Loader
---------------------------------
I pasted the disassembled code (above) into a listing file, [BOOTSTRAP-16KB.lst](BOOTSTRAP-16KB.lst),
and then ran [FileDump](/modules/filedump) to produce a [BOOTSTRAP-16KB.json](BOOTSTRAP-16KB.json) that can
be automatically pre-loaded into any machine:
filedump --file=BOOTSTRAP-16KB.lst --format=octal --output=BOOTSTRAP-16KB.json
For example, this [PDP-11/20 16Kb Machine](/devices/pdp11/machine/1120/bootstrap/debugger/machine.xml) preloads
the *Bootstrap Loader* using the `<ram>` component's optional *file* attribute:
<ram id="ram" addr="0x0000" size="0x4000" file="/apps/pdp11/boot/bootstrap/BOOTSTRAP-16KB.json"/>
I also edited [BOOTSTRAP-16KB.json](BOOTSTRAP-16KB.json) to include the following properties:
"load": 0x3FE4,
"exec": 0x3FE4,
so that the `<ram>` component knows exactly where to load and execute the file. However, the `<ram>` component can also
specify those value(s) itself, if needed:
<ram id="ram" addr="0x0000" size="0x4000" file="/apps/pdp11/boot/bootstrap/BOOTSTRAP-16KB.json" load="0x3FE4" exec="0x3FE4"/>
Finally, if you prefer octal *and* you're sure everyone will be using an ES6-capable browser, you can do this:
<ram id="ram" addr="0o00000" size="0o40000" file="/apps/pdp11/boot/bootstrap/BOOTSTRAP-16KB.json" load="0o37744" exec="0o37744"/>
All PCjs configuration files use hex and/or decimal exclusively, since those number formats have always been supported,
but as time goes by, the new octal and binary formats will be almost as universal.