First, there are no manuals for processors..
Now, to identify the speed of processor, it depends on what stage you want to identify...
If you want to identify the speed before/during purchase, you have to look at the ID in the processor box. For this, the decoding info is available at *www.cpu-world.com/info/id/AMD-Sempron-identification.html
After it is mounted and the PC assembled, you can use utilities such as CPU-Z to identify the processor.
Arun