Historically the implementation of functions and control structures has differed from those of memory. In the early days of stored program electronic computers  valves (or vacuum tubes) were employed to implement functions and control structures but valve based memory would have been very large and probably too unreliable. Consequently memory required other technology: first ultrasonic pulses in mercury tanks, then phosphor persistence on a cathode ray tube (the Williams tube) and later on magnetic core memory. Today, main memory (which is still sometimes referred to as core memory) is constructed using silicon based technology as are the functions and control structures for processors. However, the large size and regularity of memory allows different optimisations to be made.
KeywordsMercury Assure Expense Pyramid Aliasing
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