The Bootstrap Load
The Intel 4004 Microprocessor and the Silicon Gate Technology
A testimonial from Federico Faggin, designer of the 4004 and developer of its enabling technology
Quick Links:
Silicon Gate Technology
The Buried Contact
The Gilbert Hyatt Patent
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 Intelís 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.