Information for Tseng Chipset Users : general options in the XF86Config file
Previous: Basic configuration
Next: linear memory base address (MemBase) issues

8. general options in the XF86Config file

The following options are of particular interest to the Tseng driver. Each of them must be specified in the svga' driver section of the XF86Config file, within the Screen subsections of the depths to which they are applicable (you can enable options for all depths by specifying them in the Device section).

Option "noaccel"

(ET4000W32p, et6000) 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 a local or PCI bus). This option applies only to those chips where acceleration is supported.

Option "fast_dram" "slow_dram"

These options set the DRAM speed of certain cards where it applies.

The "slow_dram" option is always enabled on ET4000, and ET4000W32. If enabled, it slows down DRAM timing, which may avoid some memory-related problems. If your card starts up with a black screen (and possibly a system hang), this option might be needed.

The "fast_dram" option will cause the driver to speed up DRAM timings, which may also avoid screen-related problems (streaking, stripes, garbage, ...). It may also increase those very same effects.

All in all, these are potentially dangerous options: they could crash your machine as soon as you start the server. Use them with caution.

option "w32_interleave_off" "w32_interleave_on" (W32i, W32p)

Force memory interleaving off or on. W32i and W32p chips can increase memory bandwidth when they have 2MB or more video memory. Normally the VGA BIOS sets the W32i or W32p chip to the correct mode. If you suspect problems with memory sizing or interleaving, fooling around with these options may improve the situation. It may also make things worse. These options are not normally needed: the server will use the correct value automatically. Setting this option the wrong way will result in a completely distorted display.

option "pci_burst_off" "pci_burst_on" (W32p)

This option disables or enables PCI bursts on the W32p chip if it's a PCI card. Normally, a good BIOS will set the motherboard and the VGA card to the same setting, but if both don't match, you may experience garbage on the screen (e.g. mouse droppings). These options allow you to match the W32p burst setting to the motherboard setting.

videoram 1024 (or another value) (all chips)

This option will override the detected amount of video memory, and pretend the given amount of memory is present on the card. This is useful on cards with 2Mbyte of memory whose DRAM configuration is not compatible with the way the driver enables the upper megabyte of memory, or if the memory detection goes wrong. It must be specified in the Device section.

Clockchip "et6000" (et6000)

This enables programmable clocks, but obviously only on the et6000. It must be specified in the Device section. Normally the server will automatically use this feature when it detects an ET6000. Use it only when you suspect auto-detection is not working. Note that some frequencies may be unstable (resulting in a `Wavy' screen). Only tried and tested frequencies (like the default clocks) are guaranteed to be stable. If this happens, try a slightly different frequency in the modeline (like 0.5 MHz more or less). The monitor should still be capable of syncing to this frequency, but the clockchip may already be outside an unstable region.

Option "linear" (ET4000W32i, ET4000W32p, ET6000)

This enables linear addressing, which is the mapping of the entire framebuffer to a high address beyond system memory, making the full length of the framebuffer directly accessible. In this way, slow SVGA bank switching (where only a small fraction of the framebuffer is visible at one time) is not necessary. It enhances performance at 256 colors, and is currently required for 16bpp, 24bpp, and 32bpp.

MemBase 0xE0000000. (or a different address) (ET4000W32, ET6000)

This sets the physical memory base address of the linear framebuffer. It must be specified in the Device section. It may be required for non-PCI linear addressing configurations, and might be useful for PCI-based systems where auto-detection fails. However, almost all PCI systems will not need this.

Read the section on linear memory base address issues below!

Read the section on linear memory base address issues below! (Message repeated for a very good reason)

Use this option ONLY if you have trouble with the default MemBase used by the server, or if the server explicitly states that you must provide one.

Option "pci_retry" (ET4000W32p on PCI bus, ET6000)

This enables the PCI bus retry function, which is a performance enhancing mode for local bus or PCI bus-based systems, where the VGA controller will put the bus in a hold state (sort of like wait-states) when the server tries to start a new accelerated operation but the accelerator is still busy with the previous operation.

This is the fastest way to drive a VGA card (no busy-waiting loops needed), but it also stresses some hardware that is timing-dependent (tape drives, sound cards, etc). See also the trouble shooting section.

Information for Tseng Chipset Users : general options in the XF86Config file
Previous: Basic configuration
Next: linear memory base address (MemBase) issues