> ISA ran at 8Mhz (maybe 10Mhz or 16Mhz, memory is funny) The answer is "It depends", but it also depends on what you mean by ISA? The slots in the PC, XT, and

> ISA ran at 8Mhz (maybe 10Mhz or 16Mhz, memory is funny) The answer is "It depends", but it also depends on what you mean by ISA? The slots in the PC, XT, and AT (and clones of the appropriate vintage) tended to run synchronously with the CPU, which meant the performance of a card would depend on how fast your CPU was - well, up until the point where it was excessively overclocked and stopped working, of course. This meant that old cards wouldn't necessarily work in newer machines, given they may have been designed to work with a 4.77MHz PC. Later systems supported dividing the CPU clock to get back down to around the 8MHz range, and eventually we get to the point where the ISA slots aren't connected to the CPU at all but are bridged to PCI. But the term ISA wasn't really a thing until vendors introduced EISA as a royalty-free competitor to IBM's MCA slot architecture, and retconned the AT slot into ISA, and at that point things had pretty much settled on 8MHz. So, in that sense, ISA has always been 8MHz, even if the thing that was identical to ISA wasn't.