The PCI slots are 33.3Mhz
The AGP Slot is 66.6
PCIE Slot is 99.9 ( ok, 100 )
Now, when you overclock, the PCI / AGP / PCIE Slots also get overclocked by the same ammount.... Or by the same percentage
For example... ( Requires a minimal bit of basic math )
The CPU is 200MHZ FSB
Now, its multiplier is lets say 10
So, in english money, thats 200x10 = 2000Mhz, or 2.0Ghz
Ok, this is easy peasy so far, so why the PCIE at 101
Well, the PCI=33 the AGP = 66 and the PCIE=100 as we said earlier on, the CPU is 200 and thats the same as PCIE x 2 or in reality, the PCIE is FSB / 2
So, the PCIE will be 200/2 = 100
Now, lets say we overclock the CPU to 210 for example... This will then also overclock the PCI/AGP/PCIE so, based on the math PCIE = FSB / 2 will mean 210/2=105. So, your PCIE port will in fact not be running at 99.9 but will instead be running at 105Mhz... Forcefully overclocking the PCIE card... The PCI ports will also be running faster too... In our example the PCI will be FSB/6
So, anyway, the PCIE is at 100 as standard and adjusting the FSB will also adjust the PCIE and PCI slots...
Setting it manually to 101 will make sure it is set, while setting ig to 100 will make the system think its not been set at all and will clock it regardless.
Ok enough... That should explain if you can work through the dribble.