<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><title>8.1. Setting up MTRR</title><link rel="stylesheet" href="default.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.75.2"><link rel="home" href="index.html" title="MPlayer - The Movie Player"><link rel="up" href="video.html" title="Chapter 8. Video output devices"><link rel="prev" href="video.html" title="Chapter 8. Video output devices"><link rel="next" href="xv.html" title="8.2. Xv"><link rel="preface" href="howtoread.html" title="How to read this documentation"><link rel="chapter" href="intro.html" title="Chapter 1. Introduction"><link rel="chapter" href="install.html" title="Chapter 2. Installation"><link rel="chapter" href="usage.html" title="Chapter 3. Usage"><link rel="chapter" href="advaudio.html" title="Chapter 4. Advanced audio usage"><link rel="chapter" href="cd-dvd.html" title="Chapter 5. CD/DVD usage"><link rel="chapter" href="tv.html" title="Chapter 6. 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Video output devices</th><td width="20%" align="right"> <a accesskey="n" href="xv.html">Next</a></td></tr></table><hr></div><div class="sect1" title="8.1. Setting up MTRR"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="mtrr"></a>8.1. Setting up MTRR</h2></div></div></div><p> It is VERY recommended to check if the MTRR registers are set up properly, because they can give a big performance boost. </p><p> Do a <span class="command"><strong>cat /proc/mtrr</strong></span>: </p><pre class="screen"> <code class="prompt">--($:~)--</code> cat /proc/mtrr reg00: base=0xe4000000 (3648MB), size= 16MB: write-combining, count=9 reg01: base=0xd8000000 (3456MB), size= 128MB: write-combining, count=1</pre><p> </p><p> It's right, shows my Matrox G400 with 16MB memory. I did this from XFree 4.x.x, which sets up MTRR registers automatically. </p><p> If nothing worked, you have to do it manually. First, you have to find the base address. You have 3 ways to find it: </p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p> from X11 startup messages, for example: </p><pre class="screen"> (--) SVGA: PCI: Matrox MGA G400 AGP rev 4, Memory @ 0xd8000000, 0xd4000000 (--) SVGA: Linear framebuffer at 0xD8000000</pre><p> </p></li><li class="listitem"><p> from <tt class="filename">/proc/pci</tt> (use <span class="command"><strong>lspci -v</strong></span> command): </p><pre class="screen"> 01:00.0 VGA compatible controller: Matrox Graphics, Inc.: Unknown device 0525 Memory at d8000000 (32-bit, prefetchable)</pre><p> </p></li><li class="listitem"><p> from mga_vid kernel driver messages (use <span class="command"><strong>dmesg</strong></span>): </p><pre class="screen">mga_mem_base = d8000000</pre><p> </p></li></ol></div><p> </p><p> Then let's find the memory size. This is very easy, just convert video RAM size to hexadecimal, or use this table: </p><div class="informaltable"><table border="0"><colgroup><col><col></colgroup><tbody><tr><td>1 MB</td><td>0x100000</td></tr><tr><td>2 MB</td><td>0x200000</td></tr><tr><td>4 MB</td><td>0x400000</td></tr><tr><td>8 MB</td><td>0x800000</td></tr><tr><td>16 MB</td><td>0x1000000</td></tr><tr><td>32 MB</td><td>0x2000000</td></tr></tbody></table></div><p> </p><p> You know base address and memory size, let's setup MTRR registers! For example, for the Matrox card above (<code class="literal">base=0xd8000000</code>) with 32MB ram (<code class="literal">size=0x2000000</code>) just execute: </p><pre class="screen"> echo "base=0xd8000000 size=0x2000000 type=write-combining" > /proc/mtrr </pre><p> </p><p> Not all CPUs have MTRRs. For example older K6-2 (around 266MHz, stepping 0) CPUs don't have MTRRs, but stepping 12 does (execute <span class="command"><strong>cat /proc/cpuinfo</strong></span> to check it). </p></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="video.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="video.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="xv.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 8. Video output devices </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 8.2. Xv</td></tr></table></div></body></html>