The Pentium 4 is, of course, backward compatible with other x86 CPUs. The original design intent was to have three arithmetic units, two Floating Point Units, Two on-chip cache levels, a large off-chip cache, and an innovative instruction execution store cache that would replace the instruction cache of other x86 CPUs. A 20 stage pipeline would simplify operations thus allowing faster clock rates. In order to meet capacity/dissipation/chip size constraints, one FPU and the tightly coupled level 3 cache were eliminated during development. In addition, the level 1 cache was made smaller and faster. An improved MMX instruction set -- SSE -- is included. The result is a CPU that is somewhat difficult to compare with other X86 CPUs because its architecture is different. The consensus is that it does some things pretty well and others -- especially floating point arithmetic -- rather slowly. In some FP heavy benchmarks it is little better than the Pentium-3 that it replaces.
As with several previous Intel CPUs, performance can be enhanced by recompiling code with a compiler optimized for the Pentium-4 architecture. Experience has shown that recompilation of general purpose software does not happen for several years after the introduction of new architectures. Many current compilers have not yet been optimized for even the Pentium-3.
The Pentium-4 CPU is manufactured with a 0.18 micron process. It operates at 1.3, 1.4 or 1.5GHz. It contains a 12000 instruction execution store cache instead of the conventional instruction cache. It has a fast 8KB L1 Data Cache. There is a 256K on chip L2 Cache. The Frontside bus runs at 400MHz. Only RDRAM is supported on the initial motherboards. It uses a PGA370 Socket. It requires the Intel 850 chipset, an ATX version 2.03 Power Supply with an addition +12 volt connector, and a heatsink designed specifically for the Pentium 4. The Pentium 4 motherboards require 3.3 volts at 50 amperes. I have been unable to determine the CPU operating voltage. My guess is somewhere in the 1.2 to 1.5 volts range. CPU Power Dissipation is 55 watts.
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