Re: Covid-19
¿ªÔÆÌåÓýHi, Tony In my "toy room" I have an assembly of several 4 inch square circuit boards, bolted between a pair of 5 inch by 6 inch boards with edge connectors along one of the shorter edges. The assembly is a core memory stack with 4K, 36 bit words. Each "core" is a teeny tiny toroid with 3 wires passing through it - x and y position, and sense. If you sent a pulse through both x and y wires the sense wire would send out a pulse if the core was magnetized in 1 direction, no pulse for the other. The direction of the magnetism determined whether the core was storing a 1 or a 0. Since reading a 1 was destructive, you had to re-write every 1 after you read it. That made it very slow, but you could power the thing off and come back in 10 years and find the information still there. The Apollo computers used what was core rope memory. It is explained in depth on the (uh, oh, should I say the word?) Wikipedia page on core memory. 73 Jim W4JED On 6/17/22 19:49,
tony.volpe.1951@... wrote:
I was pretty excited to have a zx81 when they came out and well remember loading programmes from a tape recorder. They took quite a time to load, maybe ten minutes. I was disappointed that I couldn't find any practical use for the thing which cost a fair bit of money. I was reading a while ago about the way the flight computer on the early Apollo missions had programmes knitted into it by 'old ladies' The software consisted of a large box with wires 'knitted' through toroids. I don't understand how it worked exactly, but ones and zeros were stored by either passing through the toroids or being wrapped around them. |
James Daldry W4JED