The iAPX 432 (Intel Advanced Performance Architecture) is a discontinued computer architecture introduced in 1981. It was Intel's first 32-bit processor design. Design began in 1975 as the 8800 (after the 8008 and the 8080), a clean-sheet design that did not have to follow previous machine code conventions. Intel intended that the 432 would be the basis of their future offerings in the microcomputer market, replacing the older designs that had been more ad hoc solutions. The first implementation was too advanced for the semiconductor fabrication techniques of the era, and had to be implemented on two separate integrated circuits. This made it expensive to use. Combined with high prices and very low performance, the 432 ended up seeing little use. It is considered a commercial failure for Intel, and was discontinued in 1986. The loss of sales of existing designs due to the introduction of the compatible Zilog Z80 led to a 1977 effort to introduce a stop-gap solution while the 432 matured. This emerged as the 8086, which went on to form the basis of Intel processors to this day. Although some early 8086, 80186 and 80286-based systems and manuals also used the iAPX prefix for marketing reasons, the iAPX 432 and the 8086 processor lines are completely separate designs with completely different instruction sets.
Description The iAPX 432 was referred to as a "micromainframe", designed to be programmed entirely in high-level languages. The instruction set architecture was also entirely new and a significant departure from Intel's previous 8008 and 8080 processors as the iAPX 432 programming model is a stack machine with no visible general-purpose registers. It supports object-oriented programming, garbage collection and multitasking as well as more conventional memory management directly in hardware and microcode. Direct support for various data structures is also intended to allow modern operating systems to be implemented using far less program code than for ordinary processors. Intel iMAX 432 is a discontinued operating system for the 432, written entirely in Ada, and Ada was also the intended primary language for application programming. In some aspects, it may be seen as a high-level language computer architecture. These properties and features resulted in a hardware and microcode design that was more complex than most processors of the era, especially microprocessors. However, internal and external buses are (mostly) not wider than 16-bit, and, as in some other 32-bit microprocessors of the era such as the 68000, 32-bit arithmetic instructions are implemented by a 16-bit ALU, via random logic and microcode or other kinds of sequential logic. The iAPX 432 enlarged address space over the 8080 was also limited by the fact that linear addressing of data could still only use 16-bit offsets, somewhat akin to Intel's first 8086-based designs, including the contemporary 80286 (the new 32-bit segment offsets of the 80386 architecture was described publicly in detail in 1984). Using the semiconductor technology of its day, Intel's engineers weren't able to translate the design into a very efficient first implementation. Along with the lack of optimization in a premature Ada compiler, this contributed to rather slow but expensive computer systems, performing typical benchmarks at roughly 1/4 the speed of the new 80286 chip at the same clock frequency (in early 1982). This initial performance gap to the rather low-profile and low-priced 8086 line was probably the main reason why Intel's plan to replace the latter (later known as x86) with the iAPX 432 failed. Although engineers saw ways to improve a next generation design, the iAPX 432 capability architecture had now started to be regarded more as an implementation overhead rather than as the simplifying support it was intended to be. Originally designed for clock frequencies of up to 10 MHz, actual devices sold were specified for maximum clock speeds of 4 MHz, 5 MHz, 7 MHz and 8 MHz with a peak performance of 2 million instructions per second at 8 MHz.
History
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