mine was 400 and was under the impression that they were not very overclockable, so I never tried.
It was pretty fast though. I had a Pentium 450mhz at work an I do recall DVD playback being smoother on the K6... Most of the 4D games were slightly slower, but still a nice CPU.
Seems to me that I upgraded from a 166mmx that I ran at 200mhz and was able to keep the same MB. DVDs were a slideshow at 200mhz
all I really wanted to do was play DVDs which were the new hot thing without springing for a new MB, RAM, etc...
I guess the benefit to using the ISA CPU board is that you could keep the Amiga intact and even run deinterlaced it in a window if you used a USB capture card and something like AmigaManiac's svideo adapter.
Interesting idea, except I'd use something with more bandwidth then a USB port.
BTW - The original K6-IIIs were horrible overclockers.
The + components were part of the final die shrink. Eventually they only saw use in mobile devices.
The cool part was that for the first time the K6-2+ got a cache (half that of the K6-III, but still an enhancement).
I would have kept them, but long after they were irrelevant, the Germans (big AMD fanatics) were paying big bucks for one.
And you usually needed an updated bios for the K6-2+ (I guess the cache freaked out older bios'). Oddly enough, the K6-III+ was usually just a plug in.
Another cool thing, the 6X multiplier AMD substituted for the 2X.
With that, older 66 and 75MHz bus machines could do 400 to 450 MHz (on hardware that before was limited to a lot less)