- Introduction
- More than Clock Speed
- Intel's Solution
- Conclusion
- For Further Research
Like this article? We recommend
Like this article? We recommend
Like this article? We recommend
More than Clock Speed
As the introduction has already pointed out, many factors influence the performance of a given processor. Table 1 explains these factors in greater detail.
Table 1 – Processor Features and Their Impact on Performance
|
Feature |
Performance Impact |
Notes |
|
L2 cache size |
Larger cache improves performance |
All L2 cache runs at full clock speed in modern processors |
|
L3 cache |
L3 cache improves performance when present |
The Pentium 4 Extreme Edition is the first desktop processor with onboard L3 cache |
|
Front-side bus speed |
Faster FSB improves performance |
Fastest FSB speed available with Pentium 4/EE processors is 800MHz; fastest available with Athlon XP is 400MHz |
|
Efficiency per clock cycle |
More operations per clock cycle improves performance at a given clock speed and saves power |
The Pentium M and the Athlon XP are generally regarded as more efficient processors than the Pentium 4. Consequently, given models of each perform as well as Pentium 4 processors running at faster clock speeds. |
|
Improved branch predictor design |
Fewer wasted operations improves performance |
Pentium 4 Prescott, Athlon XP, and Pentium M all include various improvements in branch prediction design |
With the rise in popularity of laptop and portable computers, other factors such as voltage and the ability to run at reduced clock speeds are important considerations.
Because Intel frequently uses the same brand name (Pentium 4, Pentium M) to refer to processors which might have the same clock speed but differ in other ways, there are several situations in which it's extremely difficult to compare processors. The following sections provide two examples.
Pentium 4 Puzzlements: Prescott Versus Extreme Edition
Intel's latest processors under the Pentium 4 brand name are extremely difficult under the surface. The Extreme Edition, launched in the fall of 2003, is the first Intel desktop processor to feature onboard L3 cache, while Prescott, introduced early in 2004, is the first Pentium 4 processor to use the 90-nanometer (.09 micron) production process. Table 2 shows how these processors compare to each other and to conventional Pentium 4 processors. All of these processors use the 800MHz FSB.
Table 2 – Intel Pentium 4 Extreme Edition and Prescott Comparison
|
Processor |
Clock Speed |
L2 Cache Size |
L3 Cache Size |
Process Technology |
|
Northwood |
3.20GHz |
512KB |
--- |
.13 micron |
|
Prescott |
3.20GHz |
1MB |
--- |
.09 micron |
|
Extreme Edition |
3.20GHz |
512KB |
2MB |
.13 micron |
|
Northwood |
3.20GHz |
512KB |
--- |
.13 micron |
|
Prescott |
3.40GHz |
1MB |
--- |
.09 micron |
|
Extreme Edition |
3.40GHz |
512KB |
2MB |
.13 micron |
As Table 2 shows, the differences between the Extreme Edition, Prescott and Northwood versions of the Pentium 4 are profound, but how do they translate into real-world performance? Although Intel offers benchmarks which compare Extreme Edition to Northwood processors, it offers no such data for Extreme Edition versus Prescott. To sort out the real-world differences, you'd need to check out third-party tests from sources such as Tom's Hardware, AnandTech and others.
Mobile Muddles: Mobile Pentium 4 Versus Pentium M
Confusion over performance isn't limited to desktop computers. Although the modestly-named Pentium M (the processor used by notebook computers which use Intel's Centrino technology) has a top clock speed of only 2GHz in its latest versions, both the 2GHz and older 1.7GHz versions outperform the Mobile Pentium 4 running at 2.6GHz in both performance and battery life as measured by BAPCo's MobileMark 2002 benchmark http://developer.intel.com/products/benchmarks/notebook/index.htm
Table 3 compares the major features of the processors tested.
Table 3 – Intel Mobile Processors Compared
|
Processor |
Clock Speed |
L2 Cache Size |
FSB Speed |
Process Technology |
|
Pentium M |
1.70GHz |
1MB |
400MHz |
.13 micron |
|
Pentium M Processor 755 |
2.0GHz |
2MB |
400MHz |
.09 micron |
|
Mobile Pentium 4 |
2.6GHz |
512KB |
533MHz |
.13 micron |
As Table 3 makes clear, buying the "fastest" processor doesn't mean you'll have the 'fastest' laptop computer.