Resources

There are many sources for additional information on the Whirlwind project.

A key source for dates and project information on Whirlwind is Project Whirlwind: The History of A Pioneer Computer. By Kent C. Redmond and Thomas M. Smith. Bedford, Mass., Digital Press

The critical document for understanding the Whirlwind instruction set is the Programming Manual, 2M-0277 at http://www.bitsavers.org/pdf/mit/whirlwind/M-series/2M-0277_Whirlwind_Programming_Manual_Oct58.pdf

Documents

Many online documents from the Whirlwind program itself can be found in the following archives. All links mentioned were valid as of July 2020.

• MIT Libraries, Department of Distinctive Collections holds a major collection of Whirlwind records (MC665), including Whirlwind notebooks, engineering notes, project reports and memoranda. A portion of these documents were microfilmed (in Series 16). The documents may be seen by visiting Department of Distinctive Collections on the MIT campus in Cambridge MA.

• MITRE digitized about 1800 of the reports and memoranda, including many of the biweekly status reports, providing digital copies to MIT, which may be accessed through the MIT Libraries online archive "Dome" at: http://dome.mit.edu/handle/1721.3/37456

• Bitsavers.Org maintains an independent collection of Whirlwind documents which can be accessed at:
  http://www.bitsavers.org/pdf/mit/whirlwind

• There's another online collection of Whirlwind documents at the Defense Technical Information Center
  https://discover.dtic.mil/results/?q=whirlwind%20computer#gsc.tab=0&gsc.q=whirlwind%20computer

• The catalog for the Smithsonian Archive's collection of Whirlwind documents can be found at
  https://sova.si.edu/details/NMAH.AC.0290

Whirlwind, the Physical Artifact

• Additional material on the hardware Whirlwind-The-Physical-Artifact.pdf

Presentations

• Len Shustek’s presentation to the (virtual) Vintage Computer Festival Conference of Aug 1, 2020 describes his work on mag tape recovery, including the Whirlwind tapes at https://youtu.be/7YoolSAHR5w?t=4200

• Len’s presentation was followed by Guy Fedorkow’s talk on Whirlwind recovery: https://youtu.be/7YoolSAHR5w?t=5599

Code

• Bit-for-bit transcriptions of the Whirlwind tapes recovered so far at CHM can be found at:
  http://www.bitsavers.org/bits/MIT/whirlwind/

• A preliminary index of the paper tapes recovered is given in this spreadsheet:
  Tape-Summary-Annals-Sep30-2020.xlsx There was a prescribed format for metadata at the start of each Whirlwind tape, although it was not universally followed. This spreadsheet gives the CHM catalog number for each tape, with a title that includes any clues that might have been hand-written on the tape leader or box. The spreadsheet also includes the tape identification number and programmer’s name, if the metadata format was followed. The metadata may directly indicate whether the tape is source code or an assembled binary, otherwise the analysis script takes a guess. We also include any text strings of printable Flexowriter characters found in the tape for binary coded tapes.

• The Whirlwind simulator used in this project can be found at
  https://github.com/gfedorkow/Whirlwind-Instruction-Simulator

• Magnetic tape recovery software used in this project can be found at:
  https://github.com/LenShustek/readtape

Example Code

The code used to generate the Bounce program flow graph is given at the following link. This code is bit-for-bit identical to the binary image found on tape 102663328_fb131-0-2690_new_decoders_3of4.7ch, but given in source code format with modern labels and comments added.
fb131-0-2690_bounce-annotated.ww

While labels, assembler directives and comments are modern, the instruction format adheres to the functional model outlined in the 1958 Programming Manual, http://www.bitsavers.org/pdf/mit/whirlwind/M-series/2M-0277_Whirlwind_Programming_Manual_Oct58.pdf

The flow graph showing the bounce program as run on the first three screen-refresh cycles is given at Bounce-Flow-Graph.svg

Flow graphs such as this are extracted from simulation runs; the simulator keeps track of which instructions execute, how many times, and where branches go. Due to the common practice of modifying branch addresses dynamically, static analysis won’t tell us much. But operation of the program can be understood much more easily by watching how it actually flows.

Each bubble in the flow graph represents a single code block, i.e., sequential instructions containing no conditional branches, that have one entry and one exit point. The bubble gives the label associated with the start of the block (if any) and the first and last instructions of the block. Branches between blocks are represented by arrows with a number showing how many times the branch was taken, allowing the analyst to easily see ‘hot spots’ where the program spends the most time.

(c) Guy Fedorkow, Feb 2021