VIA Apollo Pro 133: A Camino Preview

The only limiting factor with overclocking your FSB on a chipset with official 133MHz support would be keeping your memory at a reasonable frequency.  Luckily, the Apollo Pro 133 allows you to run your memory bus at three frequencies, your FSB clock, your FSB clock + 33MHz, or your FSB clock - 33MHz.  This means that with your FSB at 133MHz, your memory can either be operating at 133MHz, 100MHz, or 166MHz but most motherboard manufacturers will disable the ability to run your memory bus at speeds greater than 133MHz.  So in the case of the 150MHz overclocked FSB frequency, you could keep your memory bus at a manageable 117MHz, a setting most high quality PC100 SDRAM will do just fine. 

The Camino chipset will have a different approach to the memory frequency.  If a motherboard manufacturer does decide to include PC133 support on their Camino based motherboard, the memory bus will operate asynchonously at 133MHz, regardless of your FSB setting.  This approach is much like how the 810 chipset keeps your memory bus at 100MHz, regardless of your FSB frequency, even if your FSB is clocked at a slower 66MHz which happens to be the case with all current un-overclocked Socket-370 810 boards.

The memory timing issues that originally plagued the Apollo Pro Plus have since been fixed with the Apollo Pro 133, so the memory performance of the Apollo Pro 133 should be much improved over its predecessor and it should be much closer to the level of the Intel BX chipset.  But we'll leave all performance discussions to the benchmarks which are coming up next...

The First 133MHz FSB CPUs

Since all Intel CPUs are now clock locked you can't simply lower the clock multiplier and use the 133MHz FSB to gain the performance boost, so the true users of the FSB frequency will start popping up with the release of the first 133MHz FSB CPUs. 

Just like with the first 100MHz FSB CPUs, the motherboard will perform a pin state detect of a previously unused pin on the processor.  In the case of the first 100MHz FSB CPUs, the pin was B21.  If B21 was set to high, the CPU was a 100MHz FSB CPU and the motherboard would make sure that the FSB frequency was set to 100MHz.  If B21 was set to low, the CPU was a 66MHz FSB CPU and the motherboard would make sure that the FSB frequency was set to 66MHz. 

With the first 133MHz FSB CPUs a reserved pin will be used to identify the specified FSB for that processor.  The pin assignment isn't known at this time but when set to high, it will indicate a 133MHz FSB CPU is present and the motherboard will then enable the 133MHz FSB.  When set to low, it will indicate either a 66 or 100MHz FSB CPU and the motherboard will then detect the state of pin B21 to determine what FSB to use. 

As with pin B21, it shouldn't be too difficult to "fool" motherboards that perform an auto-detect of what type of processor is installed in the system (whether it is a 66/100/133MHz FSB CPU) by either using a jumper setting on the motherboard (as was the case in our test system) or by possibly taping the pin using the B21 "trick" first introduced to the community by Tom's Hardware.