When you change the FSB, it's multiplied by the cpu's clock generator.
For example
A 1 GHZ TBird is a "10" clock. If you raise the fsb from 100 to 105 this is what happens.
The cpu runs at 10x105=1050 MHz
Also if the memory was PC133 it then goes to 133+5=138MHz.
SiSoft Sandra can be found at
http://www.sisoftware.co.uk/index.htm
I particularly like using Wintune for fast benchmarking to see the differences when changing system settings. It can be found here
http://www.winmag.com/scripts/download.pl/wintune/wintune_43.exe
My wintune results:
CPU (1) AMD Athlon@1313 MHz
Video Board NVIDIA GeForce2 Ultra
Video Mode 1024x768@16bits/pixel
RAM 256 MB
OS Windows 98 4.10.2222 A
Area Tested Value
CPU Integer.............. 4004.181 MIPS
CPU Floating Point....... 1646.901 MFLOPS
Video(2D)................ 175.3078 MPixels/s
Direct3D................. 592.0389 MPixels/s
OpenGL................... 488.3469 MPixels/s
Memory................... 3324.587 MB/s
Cached Disk.............. 182.1168 MB/s
Uncached Disk............ 7.280894 MB/s
In my example for my pc:
12.5 clock x 105 system bus = 1313Mhz
memory is at 133 so my ram is running at 138MHz