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Ken Shirriff

The paper that killed the 432 was "A Performance Evaluation of the Intel iAPX 432". I recently realized that one of the paper's co-authors was my former officemate twitter.com/Bob_Mayo.
archive.org/details/Performanc

11 comments
Ken Shirriff replied to Ken

The big computer architecture debate of the 1980s was RISC vs CISC, pitting Reduced Instruction Set Computers against Complex Instruction Set Computers. RISC processors were simple but fast with lots of registers, moving complexity to software. Instructions were easy to decode.

Ken Shirriff replied to Ken

Built just before RISC, the 432 took CISC to the extreme, putting everything possible into hardware rather than software: objects, garbage collection, etc. Intel called it the Silicon Operating System. With no user-visible registers, instructions were stack and memory-based.

Ken Shirriff replied to Ken

Minimizing the "semantic gap" between high-level languages and assembly language was a big thing back then. The 432 was designed for the Ada language with instructions to perform high-level operations. The Ada compiler was $30,000; we're spoiled now by open-source compilers.

Ken Shirriff replied to Ken

What if the 432 had won? Computing would be very different. Many security problems wouldn't exist. You can't have a buffer overflow because every data structure is a separate object with memory segment size enforced in hardware. You can't smash the stack or make bad pointers.
The 432 was designed around fault-tolerant multiprocessing. One chip could validate another and fail over if necessary. Computers would be much more reliable if the 432 had won.

Ken Shirriff replied to Ken

There aren't many die photos of the 432 chipset, but I made this summary from various sources. The 43201 and 43202 form the "General Data Processor". The 40203 was an attached I/O co-processor. The Bus Interface and Memory Control were for fault-tolerant multiprocessor systems.

Robert Hollingshead :donor: replied to Ken

@kenshirriff wow. I didn't know iNTEL made this and it fits neatly into my fantasy world where one could increase processing power by adding hardware to the existing hardware. You could upgrade without having to throw out the old stuff immediately. I know the nuance would kill such a thing but a person can dream.

I'm wondering if this was inspired by LISP?

Thanks for sharing

Ken Shirriff replied to Robert Hollingshead :donor:

@0xF21D I don't think there was any Lisp influence on the iAPX 432. It was inspired by object-oriented languages, specifically Ada.

Kristofer Younger replied to Ken

@kenshirriff @0xF21D my 432 had the Ada compiler. it took hours to compile “hello.adb”. had access to it at Purdue. it was 1983 i think. my summer job was learning Green Ada, at Honeywell SRC.

Ken Shirriff replied to Ken

Taking the Instruction Decoding Unit die photos was a bit tricky because the die is encased in a paperweight. Thanks to moylecroft for loaning me the paperweight.
Chips-on-board photo by @brouhaha (CC BY-SA 2.0) commons.wikimedia.org/wiki/Fil
Die photos of 43204/43205 from Intel/CHM.

Jari Komppa 🇫🇮 replied to Ken

@kenshirriff Knowing the ebb and flow of generic vs specific computing hardware, I'm pretty sure the model would have been dropped into a more generic, largely software driven system eventually and we'd have all the security problems in any case.. =)

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