alt Hacker NewsI was a kid then but my memory of 80286 was:
* Turbo was default ON and was the regular marketed speed the cpu was designed to run on, for my (dad's:) PCs it was 12 and 16mhz I think
* Turning turbo off reduced speed significantly for software written with original cpu timing in mind (I think 8088 but that was just outside of my direct experience).
So perspective on turbo button is a little bit philosophic, is it half full or half empty:). But it did not give you any EXTRA boost, like over clocking OVER manufacturer design cpu speed.
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It also hung on for some time past when it made sense. My father had a 486/33MHz that had a "turbo" button. Turning off turbo could slow the clock down but it wouldn't do anything about the fact that the 486 is still fundamentally a better processor than either the 386 or the 286, running 2-3 times faster on the same instruction stream than a 386. So even with turbo off, the programs that was nominally supposed to help with still ran much faster than they were supposed to.
This was my memory of how Turbo was explained to me - keep it on if you want to go fast. We were all learning programming, so that's what we wanted - faster computers.
The turbo button came out of "turbo XT" PC clones, rather than being some sort of defined standard. Whether or not "turbo enabled" meant "runs at normal speed" or "runs at 4.77 mhz" was entirely dependent on how your case and motherboard happened to be wired, as there was no industry-wide standardization effort at that point. There's a great video on how PC clones evolved over time here if you're interested: https://www.youtube.com/watch?v=LGoM3Sqr2-w