CAS latency 2 parts process data a little quicker than CAS latency 2.5 parts in that you have to wait a half clock cycle less for the initial data. However, after the first piece of data is processed, the rest of the data is processed at equal speeds. Latency only affects the initial burst of data. Once data starts flowing, there is no effect.Bear in mind, a clock cycle for a system properly using a PC2100 DDR module is 8 nanoseconds, so the difference between CAS latency 2 and CAS latency 2.5 for PC2100 parts is 4 billionths of a second. You probably won't be able to notice the difference.