Web-based emulator and operating environment for the Burroughs B5500 computer system.
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pkimpel Commit retro-b5500 release 1.05:
1. Implement new method to open pop-up windows that schedules pop-up opens through a queue, delaying between opens, and retrying with longer delays when the opens fail. This is to satisfy new restrictions on pop-ups introduced in Apple Safari 11.0, even when the browser is configured to enable pop-ups.
2. Remove the Application Cache facility. This API has been deprecated and will be removed from browsers.
3. Implement improved setCallback() asynchronous timing mechanism with a new Promise-based approach developed for the retro-220 emulator.
4. Correct Processor memory access logic to avoid causing an Invalid Address interrupt in Control State.
5. Correct Processor Exit Character Mode (XX00) by implementing it separately from Word Mode exits.
6. Implement separate jump mechanisms for Word and Character Mode to correct edge-case errors.
7. Make slight correction to clock counting in singlePrecisionAdd.
8. Fix bug in double-clicking the "stacker" of the card punch to extract its contents.
9. Disable I/O descriptor word count in IOUnit for card reader/punch operations; remove extraneous blank card between card-load programs from the COLDSTART-XIII.card and COOLSTART-XIII.card decks that was previously required to prevent "eating" the second program's boot card.
10. Remove extraneous whitespace from B5500FramePaper used for most text-only windows and frames.
11. Compute HPT disk latency based on current timestamp rather than a random number.
12. Correct top-of-form handling in B5500LinePrinter.
13. Correct annimation of tape reel in B5500MagTapeDrive.
14. Replace the emulator's custom bindMethod() utility routine with Function.bind().
15. Replace the emulator's custom DOM className utility routines by DOM classList methods.
16. Add P1 S and F register values to the internal tape dump caption; improve the dump tape's label records.
17. Give the annunciators on the ConsolePanel a dark gray presence when they are not lit.
18. Correct the method to "focus" the ConsolePanel window after the SPO initializes and becomes ready.
19. Clean up line delimiters in source and make consistent for Windows systems.
Latest commit c7d278d Mar 17, 2018


The Burroughs B5500 was an innovative computer system. Released first as the B5000 in 1962 and then, with minor improvements and a new disk subsystem, re-released as the B5500 in 1964, its design was a radical departure from other commercial systems of the day. Many of the concepts that it embodied were being worked on and implemented by others around the same time, but it is difficult to think of another system that pulled so many new concepts together and made them work so well in a commercially-successful product:

  • Stack- and descriptor-oriented instruction set
  • Variable-length memory segments
  • Hardware bounds checking
  • Unified integer/floating-point numeric format
  • Designed for and programmed exclusively in higher-level languages
  • Designed for and managed by a sophisticated operating system, the Master Control Program, or MCP
  • Multi-programming (multiple tasks sharing the same processor)
  • Multi-processing (multiple physical processors sharing common memory and I/O)
  • Automatic memory allocation and address relocation
  • Automatic memory segment overlay (what we now call virtual memory)
  • Use of labeled file media and automatic assignment of labeled file media to requesting programs (what we now call automatic volume recognition)

The B5500 was the foundation for the Burroughs B6000/7000/A Series, which are still produced and sold today as Unisys ClearPath MCP systems.

The main goal of this project is creation of a web browser-based emulator for the B5500. A second goal is reconstruction of the source and object code for the system.

A complete software release (Mark XIII, 1971) is presently available from the hosting site below under liberal terms of a Unisys educational/hobbyist license.

The contents of this project are licensed under the MIT License.

Related Sites URL
Getting Started http://www.phkimpel.us/B5500/webSite/HelpMenu.html
Project Blog http://retro-b5500.blogspot.com/
Web/email Forum http://groups.google.com/group/retro-b5500
Emulator hosting site http://www.phkimpel.us/B5500/
Burroughs Mark XIII Software Release http://www.phkimpel.us/B5500/webSite/SoftwareRequest.html
B5500 at retroComputingTasmania http://www.retrocomputingtasmania.com/home/projects/burroughs-b5500
Documents at bitsavers.org http://bitsavers.org/pdf/burroughs/B5000_5500_5700/
Release Downloads https://drive.google.com/folderview?id=0BxqKm7v4xBswM29qUkxPTkVfYzg&usp=sharing

This project was originally hosted on Google Code at https://code.google.com/p/retro-b5500 and moved to GitHub in June 2015.