Design Philosophy of a High Performance BiCMOS Microprocessor

概要

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The world's first 32-bit single-chip BiCMOS microprocessor has been developed. Its typical operating frequency is 70 MHz, which is 1.5 to 2.0 times faster than today's CMOS microprocessors. To achieve such a high frequency, the delay times of critical paths had to be shortened. Three design strategies are used for this. First, to reduce the delay time of the logic circuits, bipolar transistors are used effectively by limiting their use to driving a load capacitance and sensing low-level signals. Second, to accelerate memory access, the number of inter-chip communications in the critical paths is reduced. Last, to speed up the control logic, functions that may be executed slowly are eliminated from critical paths. Although the bipolar transistor is inherently larger than an MOS transistor, it had to be designed for a small chip area. This was done by using an optimal number of bipolar transistors and BiCMOS logic gates. The pro-portion of bipolar transistors used in this chip is only 1.50%, and the performance of the microprocessor depends on this low proportion.
一般社団法人情報処理学会の論文
1990-08-25