rgt http://homepage.hispeed.ch/rscheidegger/p2b_procupgrade_faq.html это, так сказать, документальное свидетельство

The last category of boards are those which need hardware modification to have a PCI clock of 33Mhz together with 133Mhz FSB. They have clock chips with 4 frequency selection inputs (such as ics9250-08), but only 3 of them are wired on the board. At least P2B-L/S/LS rev. 1.04 D03, P2B-D/DS rev. 1.06 D03 and some early revision P2B-f belong to that category. They will all run the pci clock at 44Mhz if you chose 133Mhz FSB - you're very likely to get trouble, as a lot of devices won't work at that clock frequency.

12.02.1999 A14 1.00 1008 PBF02 5D06 FS3由鐵線改為排針(Running Change) M10292 Clock generator : ICS9250-08 OLD PIIX4E (U12, SL2MY)
12.02.1999 A24 1.00 1008 PBF02 5D06 FS3由鐵線改為排針(Running Change) M10292 Clock generator : ICS9250-08 NEW PIIX4E (U12, SL37M)