The AMD A8 4555M is a quad core processor that is based on Trinity architecture. It supports hyperthreading that lets its 4 cores handle 4 threads at a time. TDP of the processor is 17 W that makes it perfect for use in ultrabook laptops. The CPU runs at 1.6 GHz and overclocks to 2.4 GHz under turbo mode. Here are its benchmark results:
1) Cinebench R10: 3681
2) 3DMark 06: 1879
3) Cinebench R11.5 (multi CPU 64 bit): 1.2
4) Passmark: 2808
As you can see, the A8 4555M is about 20 percent slower and 20 percent faster than the top end AMD A10 4655M and A6 4455M respectively. Check out AMD A10 4655 benchmark.
The AMD A6 4455M got 2602 in the Cinebench R10 benchmark app. Check out AMD A6 4455m benchmark.