Gentoo Development Guide

Arch Specific Notes -- Alpha

The Alpha port uses the alpha keyword. It focuses upon HP (formerly Compaq (formerly DEC)) hardware. This covers from ev4 (known as 21064) through ev7z (known as 21364a).

Alpha Kernel and Userland ABIs

All Alpha systems use a pure 64 bit kernel and a pure 64 bit userland.

All Alpha systems support both little and big endian — however, Linux only uses little endian.

Additional Alpha Keywording Requirements

It is generally expected that anyone who does keywording for Alpha should be on the alpha@ alias. However the Alpha team is happy if maintainers keyword their packages when they have access to Alpha hardware, although the team would like to know about it.

Alpha Instruction Set and Performance Notes

There are six basic Alpha instructions set standards:

  • ev4 or ev45. The ev4 was the first Alpha processor of the Alpha family. It featured one integer pipeline and one floating-point pipeline. The ev45 is a modified ev4 with double both Data and Instruction cache (D-Cache and I-Cache respectively); it also featured a division optimization.
  • ev5 is an evolution of the ev45. The number of pipelines was doubled and the floating-point pipelines run in 9 stages rather than in 10. The ev5 supports 3 cache levels.
  • ev56 added the BWX extension to load/store data in 8 or 16 bit quanta.
  • pca56 added a new set, MVI (Motion Video Instructions), aimed to accelerate video and audio calculations.
  • ev6 supports all extensions supported by the pca56 and a new set, FIX, meant to move data between integer and floating-point registers and for square root.
  • ev67 is an evolution of the ev6, in addition it supports a new set. CIX adds instructions for counting and finding bits.

When no -mcpu option is passed to gcc it defaults to the processor on which the compiler was built.

The -mieee flag should always be used unless you have a deep knowledge of the Alpha architecture, so the comments on Not Filtering Variables are really important on Alpha.

Notes on Alpha and PIC

General Position Independent Code policy also applies to Alpha. In fact, Alpha systems complain loudly if you try to link PIC and non-PIC code. Usually this results in errors during the compilation aborting emerge.

Contacting the Alpha Team

The Alpha team can be contacted:

  • Via Bugzilla bugs assigned to alpha@
  • Via email to the alpha@ email alias
  • Via email to the gentoo-alpha mailing list
  • Via the #gentoo-alpha IRC channel on Freenode