Here is some good news and bad news for prospective iPhone 4S owners. The bad news is that the iPhone 4S has a dual-core 1GHz CPU, but its clocked to 800 Mhz. The good news is that, even with slower clock speeds, the 4S still beats the pants off the iPhone 4 and other Android smartphones.
This information comes from AnandTech which compared the iPhone 4S and other handsets using online benchmarks. The results place the iPhone 4S at the top of the mobile phone market with benchmark scores well above the iPhone 4 and other smartphone competitors like the Samsung Galaxy S2. The only comparable device is the 8.9-inch Samsung Galaxy Tab which benchmarks very closely to the iPhone 4S.
Within the iOS family, the iPhone 4S CPU and GPU benchmarks are about 75% faster than the iPhone 4 and slightly slower than the iPad 2. These results are not surprising as the iPad 2 has the same A5 processor as the iPhone 4S, but it is clocked to the full 1GHz, not 800 MHz.