Conclusions
The preceding discussion should make it clear that the overall design approaches outlined in the first half of this chapter can be seen in the back ends of each processor. The G4e continues its “wide and shallow” approach to performance, counting on instruction-level parallelism (ILP) to allow it to squeeze the most performance out of code. The Pentium 4’s “narrow and deep” approach, on the other hand, uses fewer execution units, eschewing ILP and betting instead on increases in clock speed to increase performance.
Each of these approaches has its benefits and drawbacks, but as I’ve stressed repeatedly throughout this chapter, microarchitecture is by no means the only factor in the application performance equation. Certain properties ...
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