The Pentium III does sound like a good chip choice for a retro cyberpunk story. Like they said in “The Matrix”, 1999 was the peak of human civilization.
(586 became Pentium, so 686 would be the Pentium Pro/II microarchitecture.)
(586 became Pentium, so 686 would be the Pentium Pro/II microarchitecture.)
My favorite PC I ever built was a dual-CPU Tyan motherboard that eventually held two screaming fast Coppermines. Needed a university copy of Windows 2000 to really make them sing—the Windows 95 series never supported SMP—and it was glorious.
The Athlon was solid but less reliable, various reboots and glitches. I kind have always had a preference for Intel since then.
Some of those chipsets were fine and others were less reliable or compatible. The quality of the drivers for each chipset may also have mattered.
RISC architecture is gonna change everything.