INTEL ARCHITECTURE - 64 ( IA-64)

IA-64 (Intel Architecture-64) is a 64-bit processor architecture developed in cooperation by Intel and Hewlett-Packard, executed by processors such as Itanium. The objective of Itanium was to produce a "post-RISC era" architecture using EPIC (Explicitly Parallel Instruction Computing).

EPIC Architecture

In this system a complex decoder system study each instruction as it flows by the pipeline and sees which can be fed off to operate in parallel across the available implementation units - e.g., a sequence of instructions for performing the computations

A = B + C and

D = F + G

These will be independent of each other and will not affect to each other, and so they can be fed into two different implementations units and run in parallel. The ability to remove instruction level parallelism (ILP) from the instruction stream is necessary for good performance in a modern CPU.

Predicting which code can and cannot be divide up this way is a very difficult task. In many cases the inputs to one line are dependent on the output from a different, but only if some other condition is true. For instance, take the slight modification of the example noted before, A = B + C; IF A==5 THEN D = F + G. In this case the calculations stay independent of the other, but the second command needs the results from the first calculation in order to know if it should be run at all.