Disadvantages of P4

Price versus Performance

Pentium 4 processors are expensive. The P4s have clock speeds ranging from 1.3GHz to 1.8GHz, and their price's range from $188USD to $562USD. Computers using the P4 processors require RAMBUS RDRAM memory which cost more than the regular SDRAM (used by Pentium II, Pentium III, Celeron, Duron, and Athlon). The RAMBUS RDRAM memory system has been found to be slower in some cases than SDRAM. Last winter, SDRAM prices fell to below $50USD per 128 megabyte PC133 module. RAMBUS RDRAM is currently priced at about $99USD for 128 megabytes of PC800 memory.

For example, if people plan to install Window 2000 or any later version such as Window XP, they may want several 128 megabyte memory modules. Therefore they will be paying hundreds of dollars extra for the RDRAM.

Another drawback of the Pentium 4 processors is that they do not support the multiple instruction decoder or barrel shifter like older pentium processors did. This mean that code optimized for the earlier Pentium processors that is designed to take advantage of these performance enhancing techniques will actually run slower on the Pentium 4.

Power Consumption

The Pentium 4 processors consume more power than other processors of similar performance. This means special measures must be taken to remove the heat generated by the processor from the chip and from the enclosure. In addition, computer systems that use P4 processors require larger power supplies. The larger power supplies add more cost to a P4 base system.

As heat builds up and the temperature of the die increases, temperature sensors will reduce the clock speed to protect the processor. In a system where the processor is not adequately cooled, the processor will not run at the highest designed clock rate. To keep the processor cool, large heat sinks with integral fans are usually used. In more compact applications such as portable computers or embedded controls, huge heat sinks and fans may not be suitable due to limited space or the need for a sealed enclosure. In these cases, heat pipes or even vapor compression cooling may be required. Both of these devices cost more than heat sinks.

The requirement for extra power by the Pentium 4 processors can cause problems on the supply side too. When a power supply cannot keep up with the demands of the processor, the voltage levels will fall. This can cause errors or the computer may lock up. In portable computers, the batteries will not last as long. Computer systems that have an uninterruptible power supply may not have time to finish graceful shut down before the batteries are drained. Given the current power situation in California, this could be a real problem.