Pentium Pro

In 1995, Intel released the Pentium Pro chip, which added a new level of performance to the Pentium processor. The Pentium Pro had all the characteristics of the Pentium processor - such as a 64-bit data bus and 32-bit registers - but it increased the address bus to 36 bits, which means that the Pentium Pro can access 64GB of RAM. The speed of the Pentium Pro ranges from 120 MHz to around 200 MHz.

The Pentium Pro includes two additional features on its chip that help it outperform the original Pentium. First, the Pentium Pro chip is really a two-chip team. One chip was the actual processor (with 16K of L1 cache, like the Pentium chip), but the other chip holds an extra 256K of cache memory. Since this cache memory is physically outside of the CPU, it is considered L2 cache.

The second feature that leads to the performance gain of the Pentium Pro is what is known as dynamic execution. Dynamic execution has three stages: multiple branch prediction, dataflow analysis, and speculative execution.

• Multiple branch prediction is the idea that the processor will look ahead and predict a number of instructions that may be needed in the very near future.
• Dataflow analysis occurs when the processor looks at the instructions it has predicted will be needed next and then assigns them a logical order of execution.
• Speculative execution is the actual execution of a given instruction based on the prediction and the order of execution assigned.

The Pentium Pro chipwas implemented as a PGA chip that was placed in Socket 8.