Whirlwind

Whirlwind was one of the very first computers; it was enormously influential, for several reasons. It was the first real-time computer, unlike all the other first-generation computers, which were intended only for large-scale computations for numerical applications. It was also the first computer with core memory, which was invented for it (some time after it had first come into service; it initially used electrostatic vacuum tube main memory).

Whirlwind was built at MIT (MIT's first computer), originally for use in a flight simulator, but wound up being used to prototype the SAGE air defence system.

It was built out of vacuum tubes, and had a word size of 16 bits. It used a predecessor to microcode for internal control logic (it used a sequence of hard-wired control words for control, effectively ROM, but did not include any ability to alter the order of execution thereof.)

Instructions included a 12-bit absolute address; when its main memory later exceeded that size, a bank switching mechanism had to be added. It had only a single accumulator, and no index registers.

In common with other very early machines, its architecture was somewhat peculiar (by current standards). Its control flow capabilities were limited and primitive; it had conditional branching, but almost no support of any kind for subroutines (it did have a 'jump and save the old PC in the accumulator' instruction), and no provision for stacks. As a result of all that, extensive use was made of self-modifying code (including to return from a subroutine). It had neither interrupts or traps (but could be caused to halt on an arithmetic overflow).

The standard input/output device was a Flexowriter (very similar to a Teletype); it functioned as a printing terminal (initially only for output), and could also read and punch paper tapes. (A high-speed Ferranti photo-electric paper tape reader was also added later, as was a line printer.) Eventually, the system was enhanced with a magnetic tape drive and a drum. A vector video display and a light pen input pointing device were also added.

See also

• LINC - an important descendant of Whirlwind
• TX-0 - an earlier important descendant

External links

• Bitsavers - large collection of material
  • Whirlwind Programming Manual
  • Whirlwind I Operation Logic - good, detailed overview of the internal architecture
• Project Whirlwind - large collection of contemporary documents; e.g. bi-weekly progress reports
• MIT/CHM Whirlwind Software Recovery - Many links to other sites
  • Recovering Software for the Whirlwind Computer
  • Whirlwind, the Physical Artifact
• The Whirlwind Computer at CHM
• Gambling on Whirlwind: How the US Navy Spent $3M and got a Computer Game
• Computer-Aided Design’s Strong Roots at MIT - has a fair amount about Whirlwind