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- Newsgroups: comp.os.os2.misc
- Path: sparky!uunet!spool.mu.edu!umn.edu!csus.edu!netcom.com!samiam
- From: samiam@netcom.com (Scott Moore)
- Subject: Re: Why not standard VESA drivers??
- Message-ID: <1992Dec18.062430.7297@netcom.com>
- Organization: Netcom - Online Communication Services (408 241-9760 guest)
- References: <1992Dec17.025804.2367@sbcs.sunysb.edu>
- Date: Fri, 18 Dec 1992 06:24:30 GMT
- Lines: 40
-
- kskapin@csws3.ic.sunysb.edu (Keith T Skapinski) writes:
-
- >Why doesn't IBM (or someone else) supply VESA drivers for 800x600x16,
- >800x600x256, 1024x768x16, and 1024x768x256?
-
- >I'm sure it can be done and it would work with any SVGA cards which are
- >VESA compatible (like my Trident). I have a DOS GIF viewer called VUIMG and
- >it includes specific drivers for many SVGA cards as well as a generic VESA
- >driver which can be used with any SVGA card which is VESA compatible. The
- >VESA card works great with my Trident as well as many other cards.
-
- VESA chose to create a software driven standard for SVGA cards. The standard
- defines calls to set up a given resolution, and the most important key:
- a call to switch memory banks on the card. This is important because beyond
- 800x600x16, you can no longer fit the required video memory into a 64kb
- segment, which was all that was allocated for the video in the original
- PC plan. Now, I could stop right there, and any programmer worth his salt
- will tell you that a high speed driver does NOT stop to make an OS call
- whenever a change of vga memory location is required. I belive that this fact
- alone has kept the VESA standard from spreading even in DOS mode (for instance,
- why is there no windows driver for VESA ? windows is perfectly capable of
- using VESA BIOS calls).
- The problem is, this gets much worse when 32 bit programming is involved.
- The VESA bios was defined in terms of 16 bit code, and real mode code at that.
- If you use 32 bit code, you must switch back to 16 bit mode to make the call.
- Even using 16 bit only code, special arrangements must be made to call back
- to the bios.
- All this is not impossible, just really stupid in the light of making such a
- call during high speed display operations.
-
- Since I was one of the folks (desperately) trying to tell VESA that an all
- software standard was a big mistake, I belive that I have earned the right
- to call that standard as useless as it truly is.
-
- --
- Scott A. Moore [SAM] | "Cash is more
- samiam@netcom.com | important than your
- Santa Cruz, CA USA | mother"
- 408-423-1624 | Allan Shugart - CEO Segate Corp.
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