User:Keefpoole/sandbox

The Elliot 153 was a vacuum tube magnetic disk storage computer computer designed to perform direction finding on radio signals detected by base stations by the Elliott Brothers laboratory in Borehamwood, England. It was an extension of the Elliott 152 architecture.

The machine used 16 bit words and two's complement binary arithmetic. Instruction words were 64 bits long. A read/write cache was initially provided by two banks of 16 Williams tubes, which were later replaced by nickel delay lines. A larger storage space for data and programs was provided by a two sided magnetic disk.

Architecture

 * Disk storage

Main memory was a two sided magnetic disk with multiple read heads.

Side A had 48 tracks for program storage. Each track could hold 512 bytes with instructions stored across four tracks to allow a 64 bit instruction to be read simultaneously

Side B of the disc had 40 tracks, also of 512 bytes, which could be read an written via the S1 and S2 caches.

Side A was normally read-only; side B was read/write.


 * Instruction format

The 64 bit word is split into four 16 bit words, one for each part of the hardware:


 * Key


 * s - Spare (unused)
 * S1 - RAM store 1
 * S2 - RAM store 2
 * S3 - A constant contained in the instruction
 * Input/Output Select - Select from one of 10 paper tape readers or 3 teletypes
 * J - Jump if indicator, used with the control bits in part 3
 * Md - Multiplicand Register
 * Mr - Multiplier Register
 * Acc - Main Accumulator
 * Acc F - Function to perform on main accumulator
 * Task - used to query task selector switches on the main console
 * Control
 * if J = 1, these contain the jump condition
 * otherwise they're used for disk access