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The Bootstrap Load
At Fairchild, Faggin also built bootstrap load devices in 1970, using the silicon gate technology.
Bootstrap load was a circuit technique that allowed to build logic gates with
the output voltage equal to the full supply voltage. Bootstrap load devices
required the fabrication of good-quality capacitors on chip. At Fairchild and
also at Intel this task was thought impossible to achieve with the silicon gate
process without using an extra masking layer. Faggin showed how to make
bootstrap load devices without an extra masking layer.
Buried contact and particularly the bootstrap load, were indispensable to obtain the required speed
within the available power budget. The only other design technique with the
correct speed-power product, available at that time, was the more cumbersome
four-phase design used by Four-Phase Systems, Inc. and by Rockwell. Rockwell
used it in their first microprocessor, the PPS-4, which was completed nine
months after Intel’s 4004.
Without these vital
pieces of the technological puzzle, unknown to Hoff and Mazor, Hoff's
architecture could not have been implemented in 1970. See also Gilbert
Hyatt patent.
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