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Plan 9 - man page for vgadb (plan9 section 6)

VGADB(6)					     Games Manual					     VGADB(6)

vgadb - VGA controller and monitor database
The VGA database, /lib/vgadb, consists of two parts, the first describing how to identify and program a VGA controller and the second describing the timing parameters for known monitors to be loaded into a VGA con- troller to give a particular resolution and refresh rate. Conventionally, at system boot, the program aux/vga (see vga(8)) uses the monitor type in /env/monitor, the display resolution in /env/vgasize, and the VGA con- troller information in the database to find a matching monitor entry and initialize the VGA controller accord- ingly. The file comprises multi-line entries made up of attribute/value pairs of the form attr=value or sometimes just attr. Each line starting without white space starts a new entry. Lines starting with # are comments. The first part of the database, the VGA controller identification and programming information, consists of a number of entries with attribute ctlr and no value. Within one of these entries the following attributes are meaningful: nnnnn an offset into the VGA BIOS area. The value is a string expected to be found there that will identify the controller. For example, 0xC0068="#9GXE64 Pro" would identify a #9GXEpro VGA controller if the string #9GXE64 Pro was found in the BIOS at address 0xC0068. There may be more than one identifier attribute per controller. If a match cannot be found, the first few bytes of the BIOS are printed to help identify the card and create a controller entry. ctlr VGA controller chip type. This must match one of the VGA controller types known to /dev/vgactl (see vga(3)) and internally to aux/vga. Currently, clgd542x, et4000, mach32, mach64, s3801, s3805, s3928, vision864, and vision964 are recognized. ramdac RAMDAC controller type. This must match one of the types known internally to aux/vga. Currently att20c491, att20c492, att21c498, bt485, sc15025, stg1702, tvp3020, and tvp3025 are recognized. clock clock generator type. This must match one of the types known internally to aux/vga. Currently icd2061a, ics2494, ics2494a, s3clock, and tvp3025clock are recognized. hwgc hardware graphics cursor type. This must match one of the types known to /dev/vgactl and internally to aux/vga. Currently bt485hwgc, s3hwgc, et4000hwgc, and tvp3020hwgc are recognized. link This must match one of the types known internally to aux/vga. Currently vga and ibm8514 are recog- nized. The type vga handles generic VGA functions and should almost always be included. The type Ibm8514 handles basic graphics accelerator initialization on controllers such as the S3 family of GUI chips. The clock, ctlr, link, and ramdac values can all take an extension following a '-' that can be used as a speed-grade or subtype; matching is done without the extension. For example, ramdac=stg1702-135 indicates the STG1702 RAMDAC has a maximum clock frequency of 135MHz, and clock=ics2494a-324 indicates that the frequency table numbered 324 should be used for the ICS2494A clock generator. The functions internal to aux/vga corresponding to the clock, ctlr, link, and ramdac values will be called in the order given for initialization. Sometimes the clock should be set before the RAMDAC is initialized, for example, depending on the components used. In general, link=vga will always be first and, if appropriate, link=ibm8514 will be last. The entries in the second part of /lib/vgadb have as attribute the name of a monitor type and the value is conventionally a resolution in the form XxYxZ, where X, Y, and Z are numbers representing width, height, and depth in pixels. The monitor type (i.e. entry) include has special properties, described below and shown in the examples. The remainder of the entry contains timing information for the desired resolution. Within one of these entries the following attributes are meaningful: clock the video dot-clock frequency in MHz required for this resolution. The value 25.175 is known inter- nally to vga(8) as the baseline VGA clock rate. shb start horizontal blanking, in character clocks. ehb end horizontal blanking, in character clocks. ht horizontal total, in character clocks. vrs vertical refresh start, in character clocks. vre vertical refresh end, in character clocks. vt vertical total, in character clocks. hsync horizontal sync polarity. Value must be '+' or '-'. vsync vertical sync polarity. Value must be + or -. interlace interlaced mode. Only value v is recognized. alias continue, replacing the alias line by the contents of the entry whose attribute is given as value. include continue, replacing this include line by the contents of the previously defined include monitor type with matching value. (See the examples.) Any non-zero attributes already set will not be overwritten. This is used to save duplication of timing information. Note that value is not parsed, it is only used as a string to identify the previous include=value monitor type entry. The values given for shb, ehb, ht, vrs, vre, vt, hsync, and vsync are beyond the scope of this manual page. See the book by Ferraro for details.
Basic ctlr entry for a laptop which is only capable of a 640x480x1 resolution: ctlr # AT&T Safari NSX20 0xE0030="PhoenixVIEW(tm) VGA-Compatible BIOS Version" ctlr=vga A more complex entry. Note the extensions on the clock, ctlr, and ramdac attributes. The order here is impor- tant: the RAMDAC clock input must be initialized before the RAMDAC itself. The clock frequency is selected by the ET4000 chip. ctlr # Hercules Dynamite Power 0xC0076="Tseng Laboratories, Inc. 03/04/94 V8.00N" link=vga clock=ics2494a-324 ctlr=et4000-w32p ramdac=stg1702-135 Monitor entry for type vga (the default monitor type used by vga(8)) and resolution 640x480x[18]. include = 640x480@60Hz # 60Hz, 31.5KHz clock=25.175 shb=664 ehb=760 ht=800 vrs=491 vre=493 vt=525 vga = 640x480x1 # 60Hz, 31.5KHz include=640x480@60Hz vga = 640x480x8 # 60Hz, 31.5KHz include=640x480@60Hz Entries for multisync monitors with video bandwidth up to 65MHz. # # Multisync monitors with video bandwidth up to 65MHz. # multisync65 = 1024x768x1 # 60Hz, 48.4KHz include=1024x768@60Hz multisync65 = 1024x768x8 # 60Hz, 48.4KHz include=1024x768@60Hz multisync65 = 1024x768x1i # 87Hz, 35.5KHz (interlaced) include=1024x768i@87Hz multisync65 = 1024x768x8i # 87Hz, 35.5KHz (interlaced) include=1024x768i@87Hz multisync65 alias=vga Note how this builds on the existing vga entries.
ndb(2), vga(3), ndb(6), b.com(8), vga(8) Richard E. Ferraro, Programming Guide to the EGA, VGA and Super VGA Cards, Third Edition
The mach32 and mach64 controllers are programmed only in VGA mode, not accelerated mode, so are limited to a maximum resolution of 1024x768x8.
Adding a new monitor is usually fairly straightforward, as most modern monitors are multisync and the only interesting parameter is the maximum video bandwidth. Once the timing parameters are worked out for a partic- ular maximum video bandwidth as in the example above, an entry for a new monitor with that limit is simply # # Sony CPD-1304 # Horizontal timing: # Allowable frequency range: 28-50KHz # Vertical timing: # Allowable frequency range: 50-87Hz # cpd-1304 alias=multisync65 Even this is not necessary, as the monitor type could simply be given as multisync65.
While the use of this database formalizes the steps needed to program a VGA controller, unless you are very lucky and all the important components on a new VGA controller card are interconnected in the same way as an existing entry, adding a new entry requires adding new internal types to vga(8). At a minimum you will need the data sheets for the VGA controller chip, the RAMDAC and the clock generator. You will also need to know how these components interact. For example, a common combination is an S3 86C928 VGA chip with an ICD2061A clock generator. The ICD2061A is usually loaded by clocking a serial bit-stream out of one of the 86C928 registers. Similarly, the RAMDAC may have an internal clock-doubler and/or pixel-multi- plexing modes, in which case both the clock generator and VGA chip must be programmed accordingly. VGADB(6)

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