Sphere478 wrote on 2021-02-11, 16:25:
Aside from the rumors of the socket 5 motherboard running k6’s on interposers: Dual AMD K6 computer , I’m talking about the fastest dual socket 7 board it’s self like, was there ever one that could reach 75, 83, 100 fsb?
None of the 'super' So7 chipsets supported SMP. You're basically limited to i430NX and i430HX, and i430HX is by far the fastest of the two, both in terms of performance per clock and in attainable clock speed.
i430HX will run at 83MHz if you're lucky, boards like late rev P55T2P4 were famous for running K6Plus CPUs at 6x83=500MHz. Unfortunately the P55T2P4D doesn't feature FSB options beyond 66MHz. That is likely to be the biggest bottleneck.
Looking at boards in TH99 (not exhaustive), most i430HX dual boards only have two jumpers for 50/55/60/66MHz FSB. Only possible exception is the Tyan S1564D - there is a jumper J21 in the speed block that's alway set to open in official documents. There's a small but nonzero chance that this board has a PLL with three-bit input, and that setting this to closed would allow 68/75/83/? MHz. If so, this will be the fastest board, if the CPUs can keep up. P55C CPUs are massively overengineered, so I'd be confident that they won't be the bottleneck.
However this is speculation unless somebody can positively identify the PLL on that board and confirm what J21 does.