Microprocessor chronology

nMOS had the advantage that it could run on a single voltage, typically +5V, which simplified the power supply requirements and allowed it to be easily interfaced with the wide variety of +5V transistor-transistor logic (TTL) devices.

nMOS had the disadvantage that it was more susceptible to electronic noise generated by slight impurities in the underlying silicon material, and it was not until the mid-1970s that these, sodium in particular, were successfully removed to the required levels.

[4] By reducing the number of flawed chips, from about 70% to 10%, the cost of complex designs like early microprocessors fell by the same amount.

Early on, 4-bit processors were common, like the Intel 4004, simply because making a wider word length could not be accomplished cost-effectively in the room available on the small wafers of the era, especially when the majority would be defective.

Some unusual word lengths were also produced, including 12-bit and 20-bit, often matching a design that had previously been implemented in a multi-chip format in a minicomputer.

[43] Whereas earlier systems used a single transistor as the basis for each "gate", CMOS used a two-sided design, essentially making it twice as expensive to build.

[citation needed] As processor complexity continued to grow, power dissipation had become a significant concern and chips were prone to overheating; CMOS greatly reduced this problem and quickly took over the market.

They were replaced by the new steppers, which used high magnifications and extremely powerful light sources to allow a large mask to be copied onto the wafer at ever-smaller sizes.

By the middle of the decade, memory management units (MMUs) were becoming commonplace, first appearing on designs like the Intel 80286 and Motorola 68030.

By the end of the decade, every major vendor was introducing a RISC design of their own, like the IBM POWER, Intel i860 and Motorola 88000.

Instead of implementing expensive and impractical cooling systems, manufacturers turned to parallel computing in the form of the multi-core processor.