Pentium II vs. Pentium MMX -- you missed some of the main points; the PII is based on a Pentium Pro core -- it's much more of a pure 32-bit chip, however it does not have the 16-bit shortcomings of the original Pentium Pro, which was great for 32-bit code but actually SLOWER when running 16-bit code. The PII fixed this. Also, the PII has separate registers for floating point and MMX functions, while the P MMX uses shared registers. You still have to do a context switch, for software compatability, but the context switch in the PII is MUCH faster than in the P MMX, which actually had to save and restore the contents of a single set of registers.
What you really want is PII with 440BX chipset, giving a 100 MHz external bus. Unfortunately, it's not available yet. Many of the advantages of the faster processors (anything over 200 MHz) are being lost right now because of the bottleneck presented by memory accesses with the current and previous generations of chipsets. The 440 BX will fix this, when its available. Until then, benchmarks will suffer. I hope, but am not sure, that Intel realizes the importance of this. The relatively small performance benefits of all of the 233+ processors with current motherboard chipsets is contributing greatly to benchmarks which seem to support the belief that the AMD and Cyrix processors are as good as Intel P MMX or even PII processors (give or take, depending on the benchmark). |
