Editing Magnetic-core memory (section)

====Temperature sensitivity====
Another characteristic of early core was that the coercive force was very temperature-sensitive; the proper half-select current at one temperature is not the proper half-select current at another temperature. So a memory controller would include a temperature sensor (typically a [[thermistor]]) to adjust the current levels correctly for temperature changes. An example of this is the core memory used by [[Digital Equipment Corporation]] for their [[PDP-1]] computer; this strategy continued through all of the follow-on core memory systems built by [[Digital Equipment Corporation|DEC]] for their [[Programmed Data Processor|PDP]] line of air-cooled computers.

Another method of handling the temperature sensitivity was to enclose the magnetic core "stack" in a temperature-controlled oven. Examples of this are the heated-air core memory of the [[IBM 1620]] (which could take up to 30 minutes to reach [[operating temperature]], about {{convert|106|F}} and the heated-oil-bath core memory of the [[IBM 7090]], early [[IBM 7094]]s, and [[IBM 7030]]. Core was heated instead of cooled because the primary requirement was a ''consistent'' temperature, and it was easier (and cheaper) to maintain a constant temperature well above room temperature than one at or below it.