Information for Western Digital Chipset Users <author> The XFree86 Project, Inc. <date> 14 July 1995 <toc> <sect> Supported chipsets XFree86 supports the following Western Digital SVGA chipsets: PVGA1, WD90C00, WD90C10, WD90C11, WD90C24, WD90C30, WD90C31, WD90C33. Note that the rest of the WD90C2x series of LCD-controller chipsets are still not supported. The WD90C24 family is now supported including acceleration, adjustable clocks and a full 1MB video ram even on dual scan systems (in CRT mode). If you have trouble with the new WD90C24 support (not that we expect you will), try specifying "wd90c30" or "wd90c31" on the `Chipset' line in your <tt>XF86Config</tt> file. The WD90C24, WD90C31 and WD90C33 are supported as an accelerated chipset in the SVGA server; the accelerated features are automatically activated when a WD90C24, WD90C31 or WD90C33 is detected, or specified in the <tt>XF86Config</tt> file. <sect> Special considerations All of the Western Digital chipsets after the PVGA1 support the ability to use the memory-refresh clock as an alternate dot-clock for video timing. Hence for all of these chipsets, the server will detect one more clocks than ``normal''. What this means is that if you have an old `<tt>Clocks</tt>' line in your <tt>XF86Config</tt> file, you should comment it out, and rerun the server with the `<tt>-probeonly</tt>' option to find all of the clock values. All but the last should be the same as what you had before; the last will be new. For the WD90C00 chipset, the chipset will only support 640x480 in 256-color mode. Even though 512k of memory should allow better than 800x600, the chipset itself cannot do this. This is stated in the databook (which lists 1024x768x16 and 640x480x256 for specifications). We have also witnessed this behavior. The server will detect 17 clocks for the WD90C24, WD90C30 and WD90C31 chipsets. If you have one of these chipsets, you should let the server re-probe the clocks and update your <tt>XF86Config</tt>. There is an `<tt>Option</tt>' flag available for the <tt>XF86Config</tt> file that is specific to the Western Digital chipsets (except the WD90C24). This option is <tt>"swap_hibit"</tt>. We have determined via experimentation that the WD90C1x and WD90C3x chipsets need the high-order clock-select bit inverted, and the PVGA1 and WD90C00 need it non-inverted. This is hardcoded into the driver. Since our sample-set was rather small, we have provided the <tt>"swap_hibit"</tt> option to invert this behavior. If the clocks detected by the server show a very low last clock (under 28Mhz), then this option is likely needed. <sect> WD90C24 features These next three sections apply only if you have a WD90C24, WD90C24a, or WD90C24a2 and don't specify some other chipset in your XF86Config file. The SVGA pvga1 driver now recognizes the wd90c24 family as different from the WD90C30 and seems to resolve most of the problems people encountered when these chips were treated as WD90C3X. The new code has the following features: <itemize> <item>Locks the shadow registers at appropriate times; This should prevent scrambled displays after exiting X with dual scan screens when simultaneous or LCD display mode is selected. The code does depend somewhat on the behavior of the BIOS regarding when it locks the shadow registers, etc. <item>Allows (forces) the use of a full 1 Meg VRAM for dual scan systems when the server is started while external CRT only display is in operation. This allows 1024x768x8 resolution. <item>If the <tt/XF86Config/ file specifies a virtual screen size which requires more than 512 K VRAM when the server is started on a Dual Scan LCD, the driver will force the virtual size to 640x480. This eliminates the need to edit the <tt/XF86Config/ file when you switch from 1024x resolution on the CRT, to or from the LCD screen. If no virtual size is specified, the result will be 800x600 virtual in LCD modes and 1024x768 in CRT only mode (so you have a choice). <item>Note that on dual scan systems, you must still exit X, switch displays, and restart X to change to/from CRT only with 1 Meg videoram. This is because once the server starts, you can't change the virtual screen size. There is no way around this with the current server and the WD90C24 with dual scan displays. The WD90C24 requires half the videoram be used for a ``Frame buffer'' when the dual scan LCD is in use. <item>The new server uses the accelerated features of the WD90C24a. It is not clear from the data book if the WD90C24 also supports ALL the required features. Several people have stated that the WD90C24 is not accelerated, but the differences section of the WD90c24a data book implies that they ARE all three accelerated. The differences documented with regard to acceleration are with the type of line drawing the hardware does; Only the newer chips support the type of line drawing that MS windows wants. This may be what has caused the confusion since the accelerated windows drivers may only support the WD90c24a chips. If this turns out to be a problem with the WD90C24, acceleration can be disabled by adding the line: <verb> Option "noaccel" </verb> to the Device section of the <tt/XF86Config/ file. <item>Although the new server does not support programmable clocks in the same way as some of the other servers, 8 of the 17 clocks may be set to (almost) any value via the Clocks line. It also supports options for adjusting the VRAM clock. </itemize> <sect>WD90C24 clocks Here are some more details on the adjustable clocks: The VRAM clock (Mclk) is adjusted by adding ONE of the following option lines to the Device section of the <tt/XF86Config/: <tscreen><verb> Option "slow_dram" # Set Mclk to 47.429 MHz Option "med_dram" # Set Mclk to 49.219 MHz Option "fast_dram" # Set Mclk to 55.035 MHz </verb></tscreen> The default is to leave Mclk as the BIOS sets it. This is 44.297 on many systems. Some systems may not work properly with any of these options. If you experience ``bit errors'' on your display, reduce the Mclk speed, or don't use any of these options. The Mclk is not reset on server exit. The data book says that the maximum pixel clock is 1.6 times Mclk so you may want to experiment with higher Mclk rates if you have a fast monitor. It also says a 44.297MHz Mclk and 65MHz pixel clock is the fastest the WD90C24A2 is designed to go. However, some success has been reported with faster clocks. Don't expect all the clocks the chip can provide to work properly. The second and fourth group of 4 clocks are adjustable. That is, clocks 5, 6, 7, 8 and 13, 14, 15, 16 (counting from 1). These clocks are set by the Clocks line. Be sure to adjust the 17th (last) clock to match your Mclk. Here is a sample set of clocks lines with some clocks defined which are not directly provided by the chip. The NON-programmable clocks (1-4 and 9-12) MUST be set as indicated here. <verb> Clocks 25.175 28.322 65 36 # These are *not* programmable Clocks 29.979 77.408 62.195 59.957 # these are programmable Clocks 31.5 35.501 75.166 50.114 # these are *not* programmable Clocks 39.822 72.038 44.744 80.092 # these are programmable Clocks 44.297 # Change this if you change # Mclk above. </verb> You can program the clocks in increments of .447443 MHz. The server will warn you and adjust to the nearest increment if you specify a clock which does not fit this formula. Clocks 1-4 and 9-12 (the fixed clocks) are not constrained to this multiple, but instead are used to provide standard clocks which are not a multiple by .447443 MHz. If you probe for clocks (for example to find your Mclk), do it in CRT only mode and then add clocks lines in your <tt/XF86Config/ file. Clocks will not probe correctly in LCD mode on most systems. The BIOS on some systems may not allow switching from CRT to LCD unless the correct clock and/or mode is used. Try the following mode line for 640x480 LCD displays. <verb> ModeLine "640x480" 25.175 640 664 760 800 480 491 493 525 #CRT/LCD </verb> The following modelines have been tested with the above Clocks lines on some systems, and are provided here as examples. Some testers have experienced minor problems (snow) with the fixed 65 and 75.166 MHz dot clocks. The modelines below have been reported to circumvent these problems. Do not assume your monitor will not be damaged by any of these. <verb> # VESA 800x600@72Hz Non-Interlaced mode ModeLine "800x600.50" 50 800 856 976 1040 600 637 643 666 +hsync +vsync # 1024x768 Interlaced mode ModeLine "1024x768i" 45 1024 1048 1208 1264 768 776 784 817 +hsync +vsync Interlace # 1024x768@60Hz Non-interlaced Mode # One of the dram options may be necessary ModeLine "1024x768.65" 65 1024 1032 1176 1344 768 771 777 806 -hsync -vsync # 1024x768@60Hz Non-Interlaced mode (non-standard dot-clock) # Seems to work without dram options ModeLine "1024x768.62" 62 1024 1064 1240 1280 768 774 776 808 # 1024x768@70Hz Non-Interlaced mode (non-standard dot-clock) # May need fast_dram option ModeLine "1024x768.72" 72 1024 1056 1192 1280 768 770 776 806 -hsync -vsync </verb> <sect> Additional WD90C24 information Standard disclaimers apply. Use this driver at your own risk. If you need additional information on using XFree86 with the WD90C24 family however, you might try <url url="http://www.castle.net/˜darin" name="Darin Ernst's home page">. Darin maintains a mini-HOWTO on ``X and the WD90C24''. He was the first tester of the WD90C24 code and provided many good ideas and encouragement. You can reach Darin at <it>darin@castle.net</it> or <it>dernst@pppl.gov</it>. I only provided the WD90C24 specific code. You can reach me (Brad Bosch) at <it>brad@Lachman.com</it>. <verb> $XFree86: xc/programs/Xserver/hw/xfree86/doc/sgml/WstDig.sgml,v 3.6 1997/01/24 09:32:38 dawes Exp $ $XConsortium: WstDig.sgml /main/5 1996/02/21 17:46:29 kaleb $ </verb> </article>