Information for Chips and Technologies Users : xorg.conf Options
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3. xorg.conf Options

The following options are of particular interest to the Chips and Technologies driver. It should be noted that the options are case insensitive, and that white space and "_" characters are ignored. There are therefore a wide variety of possible forms for all options. The forms given below are the preferred forms.

Options related to drivers can be present in the Screen, Device and Monitor sections and the Display subsections. The order of precedence is Display, Screen, Monitor, Device.

Option "NoAccel"

This option will disable the use of any accelerated functions. This is likely to help with some problems related to DRAM timing, high dot clocks, and bugs in accelerated functions, at the cost of performance (which will still be reasonable on VLB/PCI).

VideoRam 1024 (or another value)

This option will override the detected amount of video memory, and pretend the given amount of memory is present on the card.

Option "NoLinear"

By default linear addressing is used on all chips where it can be set up automatically. The exception is for depths of 1 or 4bpp where linear addressing is turned off by default. It is possible to turn the linear addressing off with this option. Note that H/W acceleration is only supported with linear addressing.

Option "Linear"

When the chipset is capable of linear addressing and it has been turned off by default, this option can be used to turn it back on. This is useful for the 65530 chipset where the base address of the linear framebuffer must be supplied by the user, or at depths 1 and 4bpp. Note that linear addressing at 1 and 4bpp is not guaranteed to work correctly.

MemBase 0x03b00000 (or a different address)

This sets the physical memory base address of the linear framebuffer. Typically this is probed correctly, but if you believe it to be mis-probed, this option might help. Also for non PCI machines specifying this force the linear base address to be this value, reprogramming the video processor to suit. Note that for the 65530 this is required as the base address can't be correctly probed.

Option "HWcursor"

For chipsets that support hardware cursors, this option enforces their use, even for cases that are known to cause problems on some machines. Note that it is overridden by the "SWcursor" option. Hardware cursors effectively speeds all graphics operations as the job of ensuring that the cursor remains on top is now given to the hardware. It also reduces the effect of cursor flashing during graphics operations.

Option "SWcursor"

This disables use of the hardware cursor provided by the chip. Try this if the cursor seems to have problems.

Option "STN"

The server is unable to differentiate between SS STN and TFT displays. This forces it to identify the display as a SS STN rather than a TFT.

Option "UseModeline"

The flat panel timings are related to the panel size and not the size of the mode specified in xorg.conf. For this reason the default behaviour of the server is to use the panel timings already installed in the chip. The user can force the panel timings to be recalculated from the modeline with this option. However the panel size will still be probed.

Option "FixPanelSize"

For some machines the LCD panel size is incorrectly probed from the registers. This option forces the LCD panel size to be overridden by the modeline display sizes. This will prevent the use of a mode that is a different size than the panel. Before using this check that the server reports an incorrect panel size. This option can be used in conjunction with the option "UseModeline" to program all the panel timings using the modeline values.

Option "NoStretch"

When the size of the mode used is less than the panel size, the default behaviour of the server is to stretch the mode in an attempt to fill the screen. A "letterbox" effect with no stretching can be achieved using this option.

Option "LcdCenter"

When the size of the mode used is less than the panel size, the default behaviour of the server is to align the left hand edge of the display with the left hand edge of the screen. Using this option the mode can be centered in the screen. This option is reported to have problems with some machines at 16/24/32bpp, the effect of which is that the right-hand edge of the mode will be pushed off the screen.

Option "HWclocks"

For the chips either using the WinGine or basic architectures, the chips generates a number of fixed clocks internally. With the chips 65535 and later or the 64300, the default is to use the programmable clock for all clocks. It is possible to use the fixed clocks supported by the chip instead by using this option. Typically this will give you some or all of the clocks 25.175, 28.322, 31.000 and 36.000MHz. The current programmable clock will be given as the last clock in the list. On a cold-booted system this might be the appropriate value to use at the text console (see the "TextClockFreq" option), as many flat panels will need a dot clock different than the default to synchronise. The programmable clock makes this option obsolete and so it's use isn't recommended. It is completely ignored for HiQV chipsets.

TextClockFreq 25.175

Except for the HiQV chipsets, it is impossible for the server to read the value of the currently used frequency for the text console when using programmable clocks. Therefore the server uses a default value of 25.175MHz as the text console clock. For some LCDs, in particular DSTN screens, this clock will be wrong. This allows the user to select a different clock for the server to use when returning to the text console.

Option "FPClock8" "65.0MHz" Option "FPClock16" "65.0MHz" Option "FPClock24" "65.0MHz" Option "FPClock32" "65.0MHz"

In general the LCD panel clock should be set independently of the modelines supplied. Normally the chips BIOS set the flat panel clock correctly and so the default behaviour with HiQV chipset is to leave the flat panel clock alone, or force it to be 90% of the maximum allowable clock if the current panel clock exceeds the dotclock limitation due to a depth change. This option allows the user to force the server the reprogram the flat panel clock independently of the modeline with HiQV chipset. The four options are for 8bpp or less, 16, 24 or 32bpp LCD panel clocks, where the options above set the clocks to 65MHz.

Option "CRTClkIndx" "2" Option "FPClkIndx" "1"

The HiQV series of chips have three programmable clocks. The first two are usually loaded with 25.175 and 28.322MHz for VGA backward compatibility, and the third is used as a fully programmable clock. On at least one system (the Inside 686 LCD/S single board computer) the third clock is unusable. These options can be used to force a particular clock index to be used

Option "MMIO"

This has a different effect depending on the hardware on which it is used. For the 6554x machines MMIO is only used to talk to the BitBLT engine and is only usable with PCI buses. It is enabled by default for 65545 machines since the blitter can not be used otherwise. The HiQV series of chipsets must use MMIO with their BitBLT engines, and so this is enabled by default.

Option "FullMMIO"

The 690xx chipsets can use MMIO for all communications with the video processor. So using this option on a 690xx chipset forces them to use MMIO for all communications. This only makes sense when the 690xx is on a PCI bus so that normal PIO can be disabled.

Option "SuspendHack"

This option sets the centering and stretching to the BIOS default values. This can fix suspend/resume problems on some machines. It overrides the options "LcdCenter" and "NoStretch".

Option "18bitBus" (Chips 65540/45/46/48)

For 24bpp on TFT screens, the server assumes that a 24bit bus is being used. This can result in a reddish tint to 24bpp mode. This option, selects an 18 bit TFT bus. For other depths this option has no effect.

Chipset "ct65546" (or some other chip)

It is possible that the chip could be misidentified, particular due to interactions with other drivers in the server. It is possible to force the server to identify a particular chip with this option.

Option "SyncOnGreen"

Composite sync on green. Possibly useful if you wish to use an old workstation monitor. The HiQV internal RAMDAC's supports this mode of operation, but whether a particular machine does depends on the manufacturer.

DacSpeed 80.000

The server will limit the maximum dotclock to a value as specified by the manufacturer. This might make certain modes impossible to obtain with a reasonable refresh rate. Using this option the user can override the maximum dot-clock and specify any value they prefer. Use caution with this option, as driving the video processor beyond its specifications might cause damage.

Option "SetMClk" "38.000MHz" Option "SetMClk" "38000kHz"

This option sets the internal memory clock (MCLK) registers of HiQV chipsets to 38MHz or some other value. Use caution as excess heat generated by the video processor if its specifications are exceeded might cause damage. However careful use of this option might boost performance. This option might also be used to reduce the speed of the memory clock to preserve power in modes that don't need the full speed of the memory to work correctly. This option might also be needed to reduce the speed of the memory clock with the "Overlay" option.

Option "RGBbits" "8"

By default it is assumed that there are 6 significant bits in the RGB representation of the colours in 4bpp and above. If the colours seem darker than they should be, perhaps your ramdac is has 8 significant bits. This option forces the server to assume that there are 8 significant bits.

Option "ShowCache"

This is a debugging option and general users have no need of it. Using this option, when the virtual desktop is scrolled away from the zero position, the pixmap cache becomes visible. This is useful to see that pixmaps, tiles, etc have been properly cached.

Option "ShadowFB"

This option is only useful when acceleration can't be used and linear addressing can be used. With this option all of the graphics are rendered into a copy of the framebuffer that is keep in the main memory of the computer, and the screen is updated from this copy. In this way the expensive operation of reading back to contents of the screen is never performed and the performance is improved. Because the rendering is all done into a virtual framebuffer acceleration can not be used.

Option "NoTMED"

The new TMED DSTN dithering scheme available on recent HiQV chipsets gives improved performance. However, some machines appear to have this feature incorrectly setup. If you have snow on your DSTN LCD, try using this option. This option is only relevant for chipsets more recent than the ct65555 and only when used with a DSTN LCD.

Option "Overlay"

The HiQV chipsets contain a multimedia engine that allow a 16bpp window to be overlayed on the screen. This driver uses this capability to include a 16bpp framebuffer on top of an 8bpp framebuffer. In this way PseudoColor and TrueColor visuals can be used on the same screen. XFree86 believes that the 8bpp framebuffer is overlayed on the 16bpp framebuffer. Therefore to use this option the server must be started in either 15 or 16bpp depth. Also the maximum size of the desktop with this option is 1024x1024, as this is the largest window that the HiQV multimedia engine can display. Note that this option using the multimedia engine to its limit, and some manufacturers have set a default memory clock that will cause pixel errors with this option. If you get pixel error with this option try using the "SetMClk" option to slow the memory clock. It should also be noted that the XVideo extension uses the same capabilities of the HiQV chipsets as the Overlays. So using this option disables the XVideo extension.

Option "ColorKey" "255"

Normally the colour transparency key for the overlay is the 8bpp lookup table entry 255. This might cause troubles with some applications, and so this option allows the colour transparency key to be set to some other value. Legal values are 2 to 255 inclusive.

Option "VideoKey" "255"

This sets the default pixel value for the YUV video overlay key. Legal values for this key are depth dependent. That is from 0 to 255 for 8bit depth, 0 to 32,767 for 15bit depth, etc. This option might be used if the default video overlay key causes problems.

Option "DualRefresh"

The 69030 chipset has independent display channels, that can be configured to support independent refresh rates on the flat panel and on the CRT. The default behaviour is to have both the flat panel and the CRT use the same display channel and thus the same refresh rate. This option forces the two display channels to be used, giving independent refresh rates.

Option "Crt2Memory" "2048"

The ct69030 supports dual-head display. By default the two display share equally the available memory. This option forces the second display to take a particular amount of memory. Please read the section below about dual-head display.

Option "XaaNoScreenToScreenCopy", Option "XaaNoSolidFillRect", Option "XaaNoSolidHorVertLine", Option "XaaNoMono8x8PatternFillRect", Option "XaaNoColor8x8PatternFillRect", Option "XaaNoCPUToScreenColorExpandFill", Option "XaaNoScreenToScreenColorExpandFill", Option "XaaNoImageWriteRect", Option "XaaNoImageReadRect", Option "XaaNoPixmapCache", Option "XaaNoOffscreenPixmaps"

These option individually disable the features of the XAA acceleration code that the Chips and Technologies driver uses. If you have a problem with the acceleration and these options will allow you to isolation the problem. This information will be invaluable in debugging any problems.

Information for Chips and Technologies Users : xorg.conf Options
Previous: Supported Chips
Next: Modelines