Technologies for Processors and Memory

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Processors and memory have improved at an incredible rate. The following figure shows the relative performance per unit cost of technologies used in computers over time:

Year	Technology used in computers	Relative performance/unit cost
1951	Vacuum tube	1
1965	Transistor	35
1975	Integrated circuit (IC)	900
1995	Very large-scale integrated circuit (VLSI)	2,400,000
2020	Ultra large-scale integrated circuit (ULSI)	500,000,000,000

• Vacuum tube is a predecessor of the transistor.


• Transistor is an on/off switch controlled by an electrical signal.


• Integrated circuit (IC) combines dozens to hundred transistors into a single chip.


• Very large-scale integrated circuit (VLSI) contains hundreds of thousands to millions of transistors.

The figure below shows the growth of capacity per DRAM chip over time. The y-axis is measured in Kilobits, where K = 1,024 (2¹⁰). The DRAM industry quadrupled capacity almost every three years, a 60% increase per year, for 20 years. In recent years, the rate has slowed down and is somewhat closer to doubling every three years.