Mach64

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The Mach 64 chip is an old graphic accelerator developped by ATI. This board has basic 3D capabilites. Its support on Linux is poor but exists. This page is a walkthrough to setup Mach 64 graphics chipsets (including ATI Rage Pro) and obtain direct rendering on some of them.

Installing the basic features

2D and Xv acceleration in X can be achieved by installing xf86-video-mach64AUR.

Above driver needs root privileges to work properly, but latest Xorg servers start without root privileges. Thus, it may be needed to put the setuid bit on the Xorg server binary in order to use it as a regular user :

# chmod u+s /usr/lib/Xorg
Warning: This introduces a security breach that could allow a malicious program to obtain root privileges through an unknown vulnerability in Xorg. Use at your own risk.

3D acceleration and direct rendering

Warning: You may experience crashes if using the Mach 64 DRM driver. Direct rendering on Mach 64 is not very reliable because it never got much support. Also, this driver may have security issues and needs to run on a custom kernel with weakened safety.

On Linux, the Mach 64 chip uses the DRI/DRM system for direct rendering. The DRI part is available in the official repositories, but the DRM driver is not included in the mainline kernel. As of at least June of 2019, the default kernel configuration will not allow the Mach64 driver to successfully load and this error will be reported in the Xorg log:

$ MACH64(0): Unable to map linear aperture. Invalid argument

So the driver has to be built separately as a module for a custom kernel for which configuration option DRM_LEGACY is enabled and IO_STRICT_DEVMEM is disabled. The AUR package mach64drmAUR can build this driver.

As soon as the DRM module is built and installed, make sure you installed the DRI part mach64-dri.

Configuration

Here is an example of X configuration for a Mach 64 chip (may not be mandatory in all cases):

Section "Device"
       Identifier  "Card0"
       Driver      "mach64"
       Card        "ATI Rage Pro - Mach64"
       Option "DMAMode" "async"
       Option "ForcePCIMode" "false"
       Option "AgpMode" "2"
       Option "AgpSize" "32"
       Option "BufferSize" "2"
       Option "LocalTextures" "true"
       # Uncomment the following option if X segfaults as soon as anything using acceleration is called.
       # Option "ExaNoComposite" "true"
       # The following line will also prevent segmentation faults, but is not recommended since
       # it will disable all acceleration.
       # Option "NoAccel" "true"
       # The following enables the shadow framebuffer, which improves non-accelerated performance.
       # Use only with the "NoAccel" option.
       # Option "ShadowFB" "true"
EndSection

Details:

  • Driver: most important, allows you to use the mach64 driver.
  • DMAMode: async - default, sync (synchronous DMA), mmio (PIO/MMIO) - Dispatch Buffers.
  • ForcePCIMode: boolean, disables AGP aperture. Set to True if you have a PCI card.
  • AgpMode (AGP 1x or 2x): 1 or 2. If not set, defaults to agpgart's mode.
  • AgpSize: sets the AGP aperture in MB - The video card can access this amount of system memory using AGP and shared access in order to expand its memory capacity - enlarging this allows more textures to be stored here.
  • BufferSize: sets DMA buffer memory size in MB. Default is 2 MB. May be 1 or 2.
  • LocalTextures: boolean, by default, AGP cards will only use AGP memory for textures. To force using local card memory for textures in addition to AGP, you may set this option to true.

The AgpSize option changes the amount of system memory used for the AGP aperture and is not limited by the size of the card's on-board video memory. This memory is used for the DMA buffers BufferSize option), and the remainder is allocated for AGP textures. Of course, the AgpMode/AgpSize options are ignored for PCI cards or if ForcePCIMode is enabled on an AGP card. However, the BufferSize option can be used to change the size of the DMA buffers in system memory for both PCI and AGP cards (but it is not recommended to reduce the buffer size unless you are short on system RAM).

  • ExaNoComposite - Required to prevent segmentation faults in EXA handler.

The Modules Section:

Section "Module"
       <Your modules>
       Load  "glx"
       Load  "dri"
       Load  "vgahw"
       Load  "fb"
       Load  "int10"
       Load  "vbe"
       Load  "shadowfb"
       Load  "fbdevhw"
       Load  "exa"
       Load  "glamoregl"
EndSection

The DRI Section:

Section "DRI"
       Mode 0666 #allows anybody to use DRI
EndSection

The DRI Section (For machines where security is a concern):

Section "DRI"
       Group "video" #change to any desired group to restrict access
       Mode 0660
EndSection

Testing direct rendering

Restart X. After you are in X, you can run the command:

$ glxinfo | egrep "direct rendering|OpenGL renderer"

This should return something like this:

Direct rendering: Yes
OpenGL renderer string: Mesa DRI Mach64 [Rage Pro] 20051019 AGP 2x x86/MMX/SSE

If OpenGL renderer string says "Software Rasterizer", DRI is not working, even if direct rendering says "yes".