And the microcode was the undoing of Amdahl Corp. Gene Ahmdahl (first
guy listed on the IBM System 360 patent application... which my wife
processed) left IBM after a dispute with senior manaagement over the
price of the largest scale processors. He maintained that he could make
them much faster and could sell them much cheaper (at least in part) by
eliminating the microcode and hardwiring the instruction set.
Gene set out on his own and, true to his prediction, created a company
that began eating IBM's lunch on performance and price. Of course, his
business plan was predicated on being able to use IBM operating systems
since he couldn't afford to build his own. That, of course, was
dependent on Ahmdahl machines being 100% compatible with IBM mainframes.
It also assumed that IBM would remain benevolent and not change the
instruction set of the hardware by changing the microcode. When enough
of their lunch had been eaten by Gene IBM decided to tweak the microcode
a bit.
Mark Dapoz wrote:
> Original 8" floppies had 80K of storage. That storage was used for the
> processor microcode, not the OS. The microcode is the raw bit sequences
> used to flip the latches in the processor to implement the instruction set.
> It wasn't uncommon for a new release of the OS to come with new microcode
> which implemented some fancy new instructions needed by the new OS. I don't
> think any modern processor is microcode loadable any more, they're all hard
> wired nowdays.
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