Some motherboards, for example by Intel, have no opportunity to control the bus frequency and multiplier either at the software level and it is locked at the hardware level. But this situation is not fatal for overclocking.
To get “manual” access to the system bus, use the isolation of one of processor outputs which is responsible for installation of the bus frequency. If to cover this output with lacquer or to isolate it with a scotch tape, the bus frequency can be changed using either the software tools or some switches on a motherboard.
In Celeron and Pentium II/III processors an output B21 is responsible for auto installation of the bus frequency.
Turn Celeron on the side with no processor kernel on it, and Pentium II/III – on the side with holographic sticker on it. There is marking from B1 to B121 from each end of the contact track – a short strip of contacts is on the left while a long one is on the right. Find the 11th output on the long strip of contacts in the bottom row. This would be a contact B21 that should be isolated.