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by jandrese 2777 days ago
That's astounding. 68ks were not cheap. I assume the system then stalls for a couple of instructions to switch back to the first chip after the page fault completes? I have to assume they reached that solution after exhausting every other option.

On the other hand, this could also be used as a form of error checking. If CPU2 ever returns something different you know there was an error somewhere in the system and you can hard stop to prevent further data corruption.
2 comments
tralarpa 2777 days ago
> I have to assume they reached that solution after exhausting every other option

I assume that the 68000 was so powerful for its price (probably much cheaper than the existing mainframe CPUs) that it made this a viable solution. Or maybe the company had promised their customers a 68k-based Unix system (with the 68451 MMU) and the 68010 was delayed or too expensive and they had to find a quick solution? (I have no idea)

Btw, I was probably wrong about Sun being the company behind this. Apollo and MassComp have been mentioned in mailing lists.

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jandrese 2777 days ago
IIRC they cost around $350 each back in the 80s. That's roughly $1000 in today's dollars.

A lot of companies wanted to use them instead of the Mickey Mouse Intel chips of the day, but the price point was too severe.

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anyfoo 2777 days ago
Speaking of which: http://www.os2museum.com/wp/the-nearly-ultimate-386-board/

The article describes a motherboard with both a soldered on 386 CPU, and a separate socket for another one. This was not a multiprocessor board, to make use of the socket you were supposed to disable the onboard CPU using a jumper.

But if you plugged in a similar enough CPU without setting the jumper, it appears that both CPUs ran at the same time. And since they had the same clock and they should have no difference in behavior, the system, at least as tested, ran fine.

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