March 21st, 2005

krazy koati

You've got a friend in me

A bit I forgot from the toy store -- I knew there were dolls based on Pixar's heartwarming tale of abuse victims, Toy Story, but I'd never given them much though. It's not just me, though, that sees as really viciously sick and funny finding there's a Sid doll, right?

Maybe a month ago the question of Gemini computer core memory was raised; specifically, the question of whether (as James Tomayko's Computers in Spaceflight claims) it's possible to read a bit from core memory without destroying it. The standard core would be ``read'' by setting a bit and testing whether this changed the magnetization, which destroys what had been there.

sci.space.history had two thoughts, one poster saying a sort of twin-core could be used, the outer core for holding the bit and an inner core read from. Another found a NASA Office of Logic Design review by Robert C Ricci, A scientific study of the problems of digital engineering for space flight systems, with a view to their practical solution, Technical Note D-4224, which explains magnetic cores suffer from the limitation of only destructive-reading, ``unless more sophisticated geometries are used such as the multi-aperture devices, or Biax.'' Not a word is said about Gemini, and the more I read the less I understand.

For extra frustration, T A Heppenheimer's Development of the Space Shuttle, 1972-1981, and Dennis Jenkins's Space Shuttle talk about the shuttle's core memory and its Skylab heritage, but not just how they work. Jenkins also doesn't mention if that's still core memory flying. To sum up: I have no idea how Gemini read its memory. Happy to help.

Trivia: Rail delivered at San Francisco in 1865 cost the Central Pacific US$143.67 per ton, $51.97 of that for shipping across the Panama Isthmus. Source: Nothing Like It In The World, Stephen E Ambrose.

Currently Reading: Redcoats and Rebels: The American Revolution through British Eyes, Christopher Hibbert.