Intel Pentium II & III Processor
The Intel Pentium II / III processors based on 100MHz FSB are nowhere near as overclockable as the Intel Celeron processor, but you can still overclock these processors just like any other Intel processor. The Pentium II / III is based on a 100MHz FSB and require PC100 memory for proper operation (unless you want to run PC66 memory at 100MHz which is a BAD idea). With decent PC100 memory and cooling you should have no worries with reaching 112MHz FSB. we'll use a Pentium III 450MHz as an example, the default FSB is 100MHz, so overclocking the FSB to 112MHz x 4.5 you'll get a frequency of 504MHz. If your lucky, while using top quality PC100 memory you may be able to reach 124MHz FSB which will give you 558MHz out of a 450MHz core. Getting 124MHz is generally the best you'll out of PC100 unless you have extreme cooling happening. If you want a rock stable system, you should consider buying branded PC133 or PC150 memory. With PC133 memory in your system you will be able to reach speeds faster than 133MHz FSB and in some cases even 150MHz FSB. let's just say for 2 minutes you got lucky and got your PC133 memory operating at 150MHz, you would have your seemingly slow Pentium II / III 450MHz running at an amazing 675MHz (50% overclock). Remember though, don't get your hopes up for results like this as it hardly ever happens with standard cooled cases and processors. Shall we dream again? you've just got yourself some new PC150 memory and want overclock your Pentium II / III 450MHz to 160MHz FSB, allowing for everything to turn out well (including a BX motherboard which supports FSB settings that high) you'd have yourself a 4.5x160 = 720MHz (60% overclock) processor from your 450MHz processor - not bad, too bad this doesn't have very often though.
But let's get back to reality, generally speaking you should have no troubles reaching 133MHz FSB with Pentium II / III processors, for a rock solid system consider buying PC133 memory.