OPENCHROME(4) Kernel Interfaces Manual OPENCHROME(4)
openchrome - video driver for VIA Unichromes
openchrome is an Xorg driver for VIA chipsets that have an integrated
Unichrome graphics engine.
The openchrome driver supports the following chipsets: CLE266,
KM400/KN400, CN400, CN700, K8M800/K8N800, PM800/PN800, P4M800Pro,
VN800, PM880, K8M890/K8N890, CN896, VN896, and P4M900. The driver
includes 2D acceleration and Xv video overlay extensions. Flat panel,
TV, and VGA outputs are supported, depending on the hardware configura-
3D direct rendering is available using experimental drivers from Mesa
(www.mesa3d.org). There is also an XvMC client library for hardware
acceleration of MPEG1/MPEG2 decoding (not available on the KM/N400)
that uses the Direct Rendering Infrastructure (DRI). The XvMC client
library implements a non-standard "VLD" extension to the XvMC standard.
The current Direct Rendering Manager (DRM) kernel module is available
The driver supports free modes for Unichrome Pros (K8M800/K8N800,
PM800/PN800, and CN400). For plain Unichromes (CLE266, KM400/KN400),
it currently supports only a limited number of dotclocks, so if you are
using X modelines you must make sure that the dotclock is one of those
supported. Supported dotclocks on plain Unichromes are currently (in
MHz): 25.2, 25.312, 26.591, 31.5, 31.704, 32.663, 33.750, 35.5, 36.0,
39.822, 40.0, 41.164, 46.981, 49.5, 50.0, 56.3, 57.284, 64.995, 65.0,
65.028, 74.480, 75.0, 78.8, 81.613, 94.5, 108.0, 108.28, 122.0,
122.726, 135.0, 148.5, 155.8, 157.5, 161.793, 162.0, 175.5, 189.0,
202.5, 204.8, 218.3, 229.5. On top of this, bandwidth restrictions
apply for both Unichromes and Unichrome Pros.
Please refer to xorg.conf() for general configuration details. This
section only covers configuration details specific to this driver.
The following driver options are supported:
Option "AccelMethod" "string"
The driver supports "XAA" and "EXA" acceleration methods. The
default method is XAA, since EXA is still experimental. Con-
trary to XAA, EXA implements acceleration for screen uploads and
downlads (if DRI is enabled) and for the Render/Composite exten-
Option "ActiveDevice" "string"
Specifies the active device combination. Any string containing
"CRT", "LCD", "DFP", "TV" should be possible. "CRT" represents
anything that is connected to the VGA port, "LCD" and "DFP" are
for laptop panels (not TFT screens attached to the VGA port),
"TV" is self-explanatory. The default is to use what is
detected. The driver is currently unable to use LCD and TV
simultaneously, and will favour the LCD.
Option "AGPMem" "integer"
Sets the amount of AGP memory that is allocated at X server
startup. The allocated memory will be "integer" kB. This AGP
memory is used for the AGP command buffer (if the option
"EnableAGPDMA" is set to "true"), for DRI textures, and for the
EXA scratch area. The driver will allocate at least one system
page of AGP memory, or -- if the AGP command buffer is used --
at least 2 MB plus one system page. If there is no room for the
EXA scratch area in AGP space, it will be allocated from VRAM.
If there is no room for DRI textures, they will be allocated
from the DRI part of VRAM (see the option "MaxDRIMem"). The
default amount of AGP is 32768 kB. Note that the AGP aperture
set in the BIOS must be able to accomodate the amount of AGP
memory specified here. Otherwise no AGP memory will be avail-
able. It is safe to set a very large AGP aperture in the BIOS.
Option "Center" "boolean"
Enables image centering on DVI displays. The default is dis-
Option "DisableIRQ" "boolean"
Disables the vertical blank IRQ. This is a workaround for some
mainboards that have problems with IRQs coming from the
Unichrome engine. With IRQs disabled, DRI clients have no way
to synchronize their drawing to Vblank. (IRQ is disabled by
default on the KM400 and K8M800 chipsets.)
Option "DisableVQ" "boolean"
Disables the use of the virtual command queue. The queue is
enabled by default.
Option "EnableAGPDMA" "boolean"
Enables the AGP DMA functionality in DRM. This requires that
DRI is enabled and will force 2D and 3D acceleration to use AGP
DMA. The XvMC DRI client will also make use of this on the
CLE266 to consume much less CPU. (This option is enabled by
default, except on the K8M890 and P4M900.)
Option "ExaNoComposite" "boolean"
If EXA is enabled (using the option "AccelMethod"), this option
enables acceleration of compositing. Since EXA, and in particu-
lar its composite acceleration, is still experimental, this is a
way to disable a misbehaving composite acceleration.
Option "ExaScratchSize" "integer"
Sets the size of the EXA scratch area to "integer" kB. This
area is used by EXA as a last place to look for available space
for pixmaps. Too little space will slow compositing down. This
option should be set to the size of the largest pixmap used. If
you have a screen width of over 1024 pixels and use 24 bpp, set
this to 8192. Otherwise you can leave this at the default 4096.
The space will be allocated from AGP memory if available, other-
wise from VRAM.
Option "LCDDualEdge" "boolean"
Enables the use of dual-edge mode to set the LCD. The default
Option "MaxDRIMem" "integer"
Sets the maximum amount of VRAM memory allocated for DRI clients
to "integer" kB. Normally DRI clients get half the available
VRAM size, but in some cases it may make sense to limit this
amount. For example, if you are using a composite manager and
you want to give as much memory as possible to the EXA pixmap
Option "MigrationHeuristic" "string"
Sets the heuristic for EXA pixmap migration. This is an EXA
core option, and on Xorg server versions after 1.1.0 this
defaults to "smart". The openchrome driver performs best with
"greedy", so you should really add this option to your configu-
ration file. The third possibility is "always", which might
become more useful in the future.
Option "NoAccel" "boolean"
Disables the use of hardware acceleration. Acceleration is
enabled by default.
Option "NoAGPFor2D" "boolean"
Disables the use of AGP DMA for 2D acceleration, even when AGP
DMA is enabled. The default is enabled.
Option "NoXVDMA" "boolean"
If DRI is enabled, Xv normally uses PCI DMA to transfer video
images from system to frame-buffer memory. This is somewhat
slower than direct copies due to the limitations of the PCI bus,
but on the other hand it decreases CPU usage significantly, par-
ticularly on computers with fast processors. Some video players
are buggy and will display rendering artifacts when PCI DMA is
used. If you experience this, or don't want your PCI bus to be
stressed with Xv images, set this option to "true". This option
has no effect when DRI is not enabled.
Option "PanelSize" "string"
Specifies the size (width x height) of the LCD panel attached to
the system. The sizes 640x480, 800x600, 1024x768, 1280x1024,
and 1400x1050 are supported.
Option "Rotate" "string"
Rotates the display either clockwise ("CW") or counterclockwise
("CCW"). Rotation is only supported unaccelerated.
Option "ShadowFB" "boolean"
Enables the use of a shadow frame buffer. This is required when
rotating the display, but otherwise defaults to disabled.
Option "SWCursor" "boolean"
Enables the use of a software cursor. The default is disabled:
the hardware cursor is used.
Option "TVDeflicker" "integer"
Specifies the deflicker setting for TV output. Valid values are
"0", "1", and "2". Here 0 means no deflicker, 1 means 1:1:1
deflicker, and 2 means 1:2:1 deflicker.
Option "TVDotCrawl" "boolean"
Enables dot-crawl suppression. The default is disabled.
Option "TVOutput" "string"
Specifies which TV output to use. The driver supports "S-
Video", "Composite", "SC", "RGB", and "YCbCr" outputs. Note
that on some EPIA boards the composite-video port is shared with
audio-out and is selected via a jumper.
Option "TVType" "string"
Specifies TV output format. The driver currently supports
"NTSC" and "PAL" timings only.
Option "VBEModes" "boolean"
Enables the use of VBE BIOS calls for setting the display mode.
This mimics the behaviour of the vesa driver but still provides
acceleration and other features. This option may be used if
your hardware works with the vesa driver but not with the
openchrome driver. It may not work on 64-bit systems. Using
"VBEModes" may speed up driver acceleration significantly due to
a more aggressive hardware setting, particularly on systems with
low memory bandwidth. Your refresh rate may be limited to 60 Hz
on some systems.
Option "VBESaveRestore" "boolean"
Enables the use of VBE BIOS calls for saving and restoring the
display state when the X server is launched. This can be
extremely slow on some hardware, and the system may appear to
have locked for 10 seconds or so. The default is to use the
driver builtin function. This option only works if option "VBE-
Modes" is enabled.
Option "VideoRAM" "integer"
Overrides the VideoRAM autodetection. This should never be
Unichromes tend to be paired with several different TV encoders.
VIA Technologies VT1621
Still untested, as no combination with a Unichrome is known or
available. Supports the following normal modes: "640x480" and
"800x600". Use "640x480Over" and "800x600Over" for vertical
overscan. These modes are made available by the driver; mode-
lines provided in xorg.conf will be ignored.
VIA Technologies VT1622, VT1622A, VT1623
Supports the following modes: "640x480", "800x600", "1024x768",
"848x480", "720x480" (NTSC only) and "720x576" (PAL only). Use
"640x480Over", "800x600Over", "1024x768Over", "848x480Over",
"720x480Over" (NTSC) and "720x576Over" (PAL) for vertical over-
scan. The modes "720x480Noscale" (NTSC) and "720x576Noscale"
(PAL) (available on VT1622 only) provide cleaner TV output
(unscaled with only minimal overscan). These modes are made
available by the driver; modelines provided in xorg.conf will be
Xorg(), xorg.conf(), xorgconfig(), Xserver(), X()
Authors include: ...
X Version 11 xf86-video-openchrome 0.2.902 OPENCHROME(4)