Warlord wrote on 2020-08-02, 07:05:
very few very late 440bx boards had proper AGP/PCI dividers. So if your board doesn't have that, or you don't bother to set it […]
very few very late 440bx boards had proper AGP/PCI dividers. So if your board doesn't have that, or you don't bother to set it correctly you are effectively overclocking the AGP and PCI bus by running the memory at 133 mhz. poor stability is one thing. Frying expansion cards is another, or frying your board because the cards fry. It's not that 440bx cannot handle 133 mhz, its that majority of the boards don't have dividers, like you see on good Pentium 4 boards.
You need to take into account also the more sticks of ram you slot the more stress that is putting on the VRM.
Like as if most 440bx actually have what in modern times is considered a VRM.
Add a power hungry GPU a fe expansion cards and decide to run your fans off the motherboard headers, it's a recipe for disaster.
These are very good points . I will add the following.
The BX6 2.0 does have the required divider (4) for running PCI at 33MHz when FSB is 133MHz, do no issue here if properly configured .
As for AGP, the usual dividers for running at either at FSB speed or 2/3 FSB speed are available, so even when everything is set properly AGP base clock will be 89MHz instead of 66 MHz when running FSB at 133 MHz . This 89MHz AGP clock is a limitation common to all 440BX boards when running 133MHz FSB . There is a list of AGP cards (mostly Nvidia) unofficially able to handle 89MHz on vogons.
EDIT: See here 440BX 133Mhz FSB 89Mhz AGP Video Card Compatibility?
The stress on VRMs is one thing to consider, though, AFAIK, the Abit BX6 2.0 was a high end board overclocker-friendly board and likely has somewhat overspecced VRM design. Somebody with specific knowledge on this board may want to chime in .
The stability issue with using more than 2 or 3 RAM slots at 133MHis likely due, at least in part), to the added stress on the 440BX memory controller, IMHO .
I agree that the 440BX chipset is capable of unofficial 133MHz operation, within limits, and that how well that works in practice is dependant on motherboard implementation . AFAIK, the Asus P3B-F and Abit BX6 2.0 are two of the better ones in that respect .
Finally, I will add that Abit boards of that era are unfortunately known for often having cheap capacitors that are prone to failure and may impact stability . Recapping may be necessary .