I feel the need…OK, most people are familiar with the line from the film "Top Gun," but this same movie quote can sum up many peoples' feelings when it comes to the speed of their computer. It seems that no matter how fast their computer operates, most people wish it would run faster. Sometimes this desire is justified, particularly with users who run a lot of multimedia applications or perform video editing. But for many, the desire is simply to have the latest and greatest technology without regard to cost or actual improvements in work completion. How can an organization decide if it's worth it to upgrade their computer equipment to newer equipment using the latest processing technology? What seems like a straightforward question can easily turn into quite a puzzle when you first try to answer this question. However, using a top-down methodology can help you understand the fundamental business processes or mission goals that drive your organization, and the software applications, data characteristics, and network requirements that are necessary to support those processes. Combining this technique with performance benchmarks can enable you to determine if it's worth it to upgrade your existing technologies. To better explain this methodology, we'll use the Pentium 4, Intel's newest processor as an example and examine how a "top-down" methodology can be used to break this question down and answer it.
The Pentium 4
Intel's newest processor, the Pentium 4 debuted this year in speeds of 1.3, 1.4 and 1.5 GHz. This is the first completely new chip architecture from Intel since the introduction of the Pentium Pro in 1995. Designed for the high-end multimedia and Internet applications such as video editing, encoding MP3 files, 3D gaming and visualization applications, the new processor is based on Intel's IA-32 architecture, otherwise known as NetBurst (Intel). Why is this new architecture called NetBurst? Probably because it sounds cool and fits in well with Intel's marketing plan. However, the highlights of NetBurst and the Pentium 4, or P4 as it's commonly called, can be summarized in the following categories:
•400-MHz system bus
•Advanced transfer cache
•Execution trace cache
•Hyper-pipelined technology
•Rapid -execution engine
•Advanced dynamic execution
•Enhanced floating-point and multimedia unit
To better understand some of the potential improvements of upgrading to this processor, each of the categories are discussed in further detail.
400-MHz System Bus - The P4's front-side bus, or system bus, is only clocked at 100 MHz and transfers 64-bits of data per clock cycle with an 8 byte data bandwidth. However, the new bus is what Intel calls quad-pumped, meaning there are 4 channels for the data to travel through. This translates to 8 bytes * 100 million/s * 4 = 3200MB/s. This is a tremendous improvement over the Pentium III and is currently the highest desktop system bus available.
Advanced Transfer Cache - This also known as Level 2 or L2-cache. The L2 cache on the P4 is identical in size to the Pentium III at 256 KB. However, the Pentium 4's L2-cache uses 128 byte cache lines that are divided into two 64-byte sections. Thus the L2-cache reads data 64 bytes at a time, which improves performance during burst transfers but can reduce performance if only one byte out of the 64 is actually required.
Execution Trace Cache - The P4's trace cache can be viewed as an L1 instruction cache that lies behind the decoders. In the P4, unlike the Pentium III, the executable instructions are of a defined size. Once in the trace cache, the P4 saves time by not having to re-decode repeating instructions. The trace cache ensures that the processor pipeline is continuously fed with instructions, decreasing the chance of the processor having to wait on the decoder units. This is especially