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<?xml version="1.0" encoding="UTF-8"?>
<guide self="archs/sparc/">
<chapter>
<title>Arch specific notes — SPARC</title>
<body>
<p>
The SPARC port uses the <c>sparc</c> keyword. It focuses on <c>sun4u</c>
hardware (Sun UltraSparc systems with <c>v9</c> CPUs). <c>v8</c> processors
and 2.4 kernels should still work with Gentoo, but they are no longer supported
by the Gentoo/SPARC team.
</p>
<p>
SPARC systems are notoriously strict on aligned access: this is the most common
type of bug seen on SPARC (other than big-endian related issues), causing a
<c>SIGBUS</c> signal to be sent to the errant process. Known issues should be
linked to
<uri link="https://bugs.gentoo.org/371525">the related tracker bug</uri>.
</p>
<p>
This is usually due to supposedly clever pointer casts and type punning tricks
by the code authors.
</p>
</body>
<section>
<title>SPARC kernel and userland ABIs</title>
<body>
<p>
<c>v9</c> systems use a pure 64 bit kernel and a pure 32 bit userland. This can
cause portability problems when working with low level software if the kernel
does not provide working 32 bit compatibility interfaces.
</p>
<p>
<c>v8</c> systems use a pure 32 bit kernel and a pure 32 bit userland.
</p>
<p>
All of the above SPARC systems are big endian, nevertheless the <c>v9</c>
architecture also utilizes little-endian instructions to access data on PCI
buses.
</p>
</body>
</section>
<section>
<title>Additional SPARC keywording requirements</title>
<body>
<note>
This section is in addition to the guidelines in
<uri link="::keywording/#Keywording on upgrades"/>. It discusses
<e>additional</e> requirements for the SPARC architecture.
</note>
<p>
For a package to have the <c>~sparc</c> keyword added, the following additional
items must generally hold:
</p>
<ul>
<li>
The package must have been tested by an arch team member (or someone with
permission from the arch team) on a <c>v9</c> system.
</li>
</ul>
<p>
It is generally expected that anyone who does keywording for SPARC should be on
the <c>sparc@</c> alias.
</p>
</body>
</section>
<section>
<title>SPARC instruction set and performance notes</title>
<body>
<p>
There are three basic SPARC instruction set standards.
</p>
<ul>
<li>
<c>v7</c> is the original instruction set used in very old hardware. Gentoo does
not ship <c>v7</c> capable stages, however a sufficiently crazy person could in
theory run Gentoo on a <c>v7</c> machine.
</li>
<li>
<c>v8</c> is an extension of <c>v7</c> with added support for hardware integer
multiplication and division. Last time Gentoo sparc32 (<c>sun4m</c>) stages
were available was on 2006.1 release.
</li>
<li>
<c>v9</c> adds in 64 bit support and a large number of performance-enhancing
features. Gentoo sparc64 (<c>sun4u</c>) stages are <c>v9</c>.
</li>
</ul>
<p>
In addition, individual CPU implementations have slight differences <d/> for
example, HyperSparc CPUs have relaxed requirements when it comes to scheduling
certain instructions. These are relatively minor differences.
</p>
<p>
If <c>gcc</c> is invoked without any <c>-mcpu</c> parameter, it will generate <c>v7</c>
code. Depending upon the application, this can be anywhere up to five times
slower than <c>v9</c> code when running on an UltraSparc <d/> cryptographic and
graphics applications which make heavy use of integer multiplication and
division are especially badly hit. For this reason, the comments in
<uri link="::general-concepts/user-environment/#Not filtering variables"/>
are especially important on SPARC.
</p>
</body>
</section>
<section>
<title>Contacting the SPARC team</title>
<body>
<p>
The SPARC team can be contacted:
</p>
<ul>
<li>
Via Bugzilla bugs assigned to <c>sparc@</c>
</li>
<li>
Via email to the <c>sparc@</c> email alias
</li>
<li>
Via email to the <c>gentoo-sparc</c> mailing list
</li>
<li>
Via the <c>#gentoo-sparc</c> IRC channel on Libera.Chat
</li>
</ul>
</body>
</section>
</chapter>
</guide>
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