Some people think that if they only buy the most powerful computer available, they won't have to upgrade for a long, long time. These people forget, however, that a generation of computer technology lasts less than a year. Here's something else to consider. While a faster processor will usually increase the speed of your system, merely doubling the processor speed usually will not double the performance. That's because there are a lot of other limiting factors.
Memory is a prime example.
Even if buying the top machine did double your performance, however, it still might not make as big a difference as you might think. If your software performs any given task in under a second, doubling its speed saves you less than half a second. Soon, we'll see 150 MHz and 166 MHz versions. They cost only a little more than the slowest models, and deliver performance that is not much worse than that of the priciest chips. No products change as quickly as computers.