WARNING this is completely untested -- you may damage your hardware attempting this!
This server may work with true XGA compatible boards. However, this is completely untested. You should be familiar with XGA internals, be willing to do some debugging, and be willing to risk your hardware. If you know of any vendors still producing XGA clones for the (E)ISA, VESA, or even PCI bus, let me know. Some bits of crude POS probe code exist, but have proved useless for AGX based boards and are currently disabled. A few people have made attempts to use XGA cards, but no one has reported success.
To attempt using an XGA compatible board, you will need to specify several parms:
XGA instance number, this is the minimum that will need to be specified for XGA boards.
The I/O address of the the XGA general control registers. Typically 0x21i0, where i is the instance number.
Address of the graphics engine's memory mapped control registers. Typically: 0xC1C00 + (ext_mem_addr * 0x2000) + (instance * 0x80) where ext_mem_address is the high order 4-bits of POS register 2 (the server assumes zero).
While this was intend to override the POS register base address, until someone with an XGA card can complete and test POS register probing, it will be used to specify the value of POS register 4. POS register 4 contains bits 31-25 of the XGA's video memory system address. The value is shifted one place to the left so that it is contained in bits 7-1 of POS register 4. Bit 0 of the register is not used by this server as the XGA's linear aperture is not used (however, the graphics engine must be configured with this address).
The XGA-2 has programmable clocks up to 90Mhz, this, and the XGA color table code are the most notable areas of XGA unique code that have had absolutely no testing in any form. The XGA-1 clocks selection is a subset of the AGX mechanism and but recent reports from someone trying to get an XGA going indicates that probing doesn't work. To specify programmable clocks for the XGA-2, specify any of the programmable clock option values on the clocks line (e.g. "icd2061a", doesn't matter which). Standard XGA-1 clock values can also be used with the XGA-2.
$XConsortium: agx.sgml,v 1.4 95/01/27 16:14:35 kaleb Exp $ $XFree86: xc/programs/Xserver/hw/xfree86/doc/sgml/agx.sgml,v 3.7 1995/01/28 16:02:54 dawes Exp $
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