Welcome to decuser’s blog
Topics on this blog include computing, retro-computing, operating systems, math, and whatever other technical subjects I happen to be exploring that I find interesting enough to take and share notes about.
Posts
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A tutorial introduction to programming PDP-11 Macro-11 Assembly in RT-11 v5.3
A tutorial about how to do assembly language programming and debugging in RT-11v5.3 running on a SimH PDP-11.
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Tutorial - Setting up RT-11 v5.3 on SimH PDP-11
A tutorial about how to set up an RT-11 v5.3 in a SimH PDP-11 instance in Support of MACRO-11 Assembly Development and Experimentation.
The RT-11 is a small, single-user, real-time operating system for the PDP-11, 16-bit family of computers. It is simple to install and it works fine with SimH, it just takes some getting used to. If you have ever used DOS, it will seem mildly familiar. This tutorial is enough to get you started with RT-11, but it is by no means a complete introduction. Once you have the environment up and running, I recommend that you read Introduction to RT-11 referenced below. That document will take the reader through a number of exercises to get more familiar with the operating system.
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PDP-11 Bootstrap loaders - some analysis
This note provides some short analyses of several of the PDP-11 bootstrap loaders used to install the Research Unix Sixth edition. It is a work in progress…
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PDP-11 BASIC, booting the hard way
This note describes the process of running PDP-11 Basic from the PDP-11 Basic Paper Tape System. It is informed and inspired by Malcolm Macleod’s webpage entitled, “PDP-11 Paper Tape BASIC” located at http://www.avitech.com.au/ptb/ptb.html. It describes the process, step by step, of keying in the bootstrap loader, running it to load the absolute loader from paper tape stored in bootstrap loader format, and then running the absolute loader to load the PDP-11 BASIC program from paper tape stored in absolute loader format.
To learn more about how the bootstrap loader works, see my prior note
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Analysis of the PDP-11 bootstrap loader code
This note describes, in detail, how the bootstrap loader code operates. While it is only 14 words, it is not trivial to understand. The bootstrap loader is self-modifying code
The note is a work in progress. It begins by describing the first iteration where the loader loads a single byte from the tape reader. In this case the byte is octal 351, which is the first byte of the absolute loader and is the tape leader byte. Octal 351, when read by the bootstrap loader has the effect of causing the boot strap loader to overwrite a portion of itself that results in no change to its memory contents. Any other value, when read will cause the bootstrap loader to begin copying bytes into a memory location prior to the bootstrap loader itself and continuing to copy bytes until the bootstrap loader overwrites itself with the contents of the loaded program. Programs that are bootstrap loader programs contain a footer that restores they original bytes of the bootstrap loader except for the starting location.
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Adding tar to Research Unix Version 6 Running on a PDP 11/40 in SimH
This note explains an approach to getting a working version of tar running on Research Unix Version 6 (v6) running in a SimH PDP-11/40 Simulator.
NOTE: After working at this for a bit, it is clear to me that while this is workable as a solution to move files from v6 to v7, it is not workable as a true tar for v6. The program has difficulty with directories, timestamps and such when working natively on v6. The issues are not with the instructions outlined below, but rather with limitations of the original program as delivered with v7. More investigation is required to understand its limitations.
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Installing and Using Research Unix Version 7 in SimH PDP-11/45 Emulator
This note is intended to document the process of running v7 in a PDP-11/45 emulated environment. A previous note covers v6 originally posted November 23, 2015 and there is a more recent note covering v7.
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Installing and Using Research Unix Version 6 in SimH PDP-11/40 Emulator
This note is intended to document the process of running v6 in a PDP-11/40 emulated environment. A subsequent note covers v7
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Raspberry Pi B+, i2c, and DS3231 RTC
Here are some notes on how to get your pi talking to a cheapo DS3231 Realtime clock using nothing more than a pi, an ethernet cable (for downloads), a serial cable, and an RTC.
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HelloMono - Mono on Windows XP
An article I wrote back in the day (2004-05-06)and published on CodeProject. The article is rated 4.37 and has been viewed more than 212k times as of November 30, 2022.
https://www.codeproject.com/Articles/6977/HelloMono-Mono-on-Windows-XP