Friday, July 10, 2009

Memories are made of this


It is about four inches square. A better photograph would show it to be a grid of hundreds of tiny ferromagnetic ceramic donuts, each one strung through with four thin wires (see inset from web). It's been laying around my house since the early days of computers.

Each of the tiny donuts can be magnetized one of two ways -- clockwise or counterclockwise -- depending on the direction of the current that is sent through the wires. Each donut then can store a one or a zero, and the direction of magnetization can be read and rewritten by sending an appropriate current through the wires. Six-hundred or so bits of computer memory. Core memory, it was called.

Compare this early example of computer memory to the little postage-stamp-sized card in your digital camera that stores 4 gigabytes of data. Fifty-million times more data in a fraction of the space.

Each bit of the earliest magnetic core memory cost about a buck. At that rate, your camera card would cost $32 billion.

Or what about that flash drive you stick in the USB port, with its 64 gigabytes of memory.

Soon, the hard drive in your computer will be replaced by flash memory, if it hasn't been already.

Always smaller, denser, cheaper -- inevitably approaching the density and capacity of the human brain.