I think that the ISA divider is controlled by the same clockgen that produces the PCI clock. (That is, if the ISA clock is synced to the FSB, I don't think it is). Spec is 8.333 MHz. This is 100/12. Or, PCI/4. (PCI on 100MHz is 100/3=33.333). On 133, PCI is 133/4. So, PCI/4 still stands for ISA.
In conclusion since I am very drunk, it's :30 past midnight and I'm watching Seinfeld, I believe now that the ISA bus is simply the PCI bus divided by 4.