egisin@mks.com (Eric Gisin) (10/04/89)
We have a number of Orchid Designer VGA boards in 286 & 386 AT machines. Most of them (5 out of 8) will not go into the high res, 256 colour, modes. The low res, 256 colour, mode 13 works on all of them. The symtoms are different each time you set the mode, and include incorrect scan rates or scrambled images. Some boards will set the modes correctly sometimes. The problems persist when you move the card between slots and between 6, 16, and 20Mhz machines. I would guess the boards are bad, except that one of them works sometimes when video bios is shadowed, and never works in the high res modes without shadowing. That may suggest that there may be bus timing problems. Has anyone else had these problems? Are the boards bad or are there timing problems? It it is timing problems, how could they affect only 3 modes? (bios mode switching is done with a series of "outb"s to set VGA registers). If you have one of these VGA boards and want to test it, install and configure the vmode program from the floppy. Now alternate the commands "vmode 12" and "vmode 2e" to switch between the 16 and 256 colour, 640x480 graphics modes. The screen and font should be identical, except mode 2e scolls very slowly. You can also test it with the VPIC gif viewer from comp.binaries.ibm.pc. If mode 12 works and 2e does not, you have the same problem we do. PS. What is the difference between the plain Designer and the Designer 800. The 800 has a larger card and better documentation, but they are both 8 bit, 512K, and have exactly the same modes. There is a big price difference, though.