Remember the iAPX 432?

Remember the iAPX 432?

Posted Jan 18, 2007 22:27 UTC (Thu) by JoeBuck (subscriber, #2330)
In reply to: Remember the iAPX 432? by BrucePerens
Parent article: LCA: Andrew Tanenbaum on creating reliable systems

I've met the former Intel exec who was in charge of the 432. The 432 is a great example of an interesting failure, interesting because of how much it taught people and the influence that it had on the industry. It certainly influenced David Patterson, father of RISC (and no, the x86 didn't really defeat RISC, since all modern x86 machines are RISC internally, with the CISC instructions translated to RISC micro-ops on the fly).

The idea of the 432 was to close the semantic gap, by directly supporting high-level language constructs in hardware. The VAX architecture had similar ideas, though the VAX didn't take things as far. The problem is that you pay through the nose for this stuff, and there's no way to avoid the penalty, even in cases where the compiler can easily prove that the condition the hardware is protecting against can't happen. Complex microcode is needed to handle all the possible corner-cases.

The end result is that even though the hardware has specialized stuff to handle the complex language constructs, much simpler hardware beat the pants off of heavyweight monstrosities, with vastly less silicon area and power.

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