STORAGE
Reading edition
The internal Memory System for PDP-3 consists of modules of 4096 words of coincident current magnetic core storage. Each word has 36 bits. The memory modules operate with a read-rewrite cycle time of 5 microseconds. The driving currents of the memory are automatically adjusted to compensate for normal room temperature variations.
Each core memory module consists of the memory stack, the required X and Y switches, the X and Y current sources and sense amplifiers for that stack.
The Memory Address Register, the Memory Buffer Register, and the Memory Timing Controls are considered to be part of the Central Processor. The standard PDP-3 Memory Address Register configuration is built to allow up to 8 modules of core memory (32,768 words). There is a space in the addressing section of the machine to allow expansion of the addressing by a factor of eight for a total addressing capacity of 262,144 memory registers.
The Core Memory may be supplemented by Magnetic Tape Storage. This is described under Input-Output.