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USENIX 2005 Annual Technical Conference, General Track — Abstract

Pp. 265–278 of the Proceedings

Awarded General Track Best Student Paper!

Itanium—A System Implementor's Tale

Charles Gray, University of New South Wales; Matthew Chapman and Peter Chubb, University of New South Wales and National ICT Australia; David Mosberger-Tang, Hewlett-Packard Labs; Gernot Heiser, University of New South Wales and National ICT Australia


Itanium is a fairly new and rather unusual architecture. Its defining feature is explicitly-parallel instruction-set computing (EPIC), which moves the onus for exploiting instruction-level parallelism (ILP) from the hardware to the code generator. Itanium theoretically supports high degrees of ILP, but in practice these are hard to achieve, as present compilers are often not up to the task. This is much more a problem for systems than for application code, as compiler writers' efforts tend to be focused on SPEC benchmarks, which are not representative of operating systems code. As a result, good OS performance on Itanium is a serious challenge, but the potential rewards are high.

EPIC is not the only interesting and novel feature of Itanium. Others include an unusual MMU, a huge register set, and tricky virtualisation issues. We present a number of the challenges posed by the architecture, and show how they can be overcome by clever design and implementation.
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