The main difference between the Intel Atom N270 1.6GHz and the Atom N280 1.66GHz is the FSB. The latter has 667MHz while the former has 533MHz. The clock speed difference is merely 67 Megahertz. See below our comparative chart.
A quick run thru Super Pi showed the N280 (1.66GHz) edging slightly faster than the N270 (1.6GHz). That extra 60MHz is evident in the results.
The main difference between the N270 and the N280 is actually in the bus speed (133Mhz vs. 166MHz) as shown in the CPUId below:
Also check out our comparison of the Atom Z530 vs. the N270.
