GD.SAR@forsythe.stanford.edu (Sandy Rockowitz) (09/14/90)
In a recent posting, David Goings (goings@felix.UUCP) wrote of his travails in getting an ATI VGA-16 card to work with a mono card under OS2 v 1.2. He wrote in part: > The ATI support personnel told me this gem: > > You have to set the ATI board up for 8-bit bus use if there is a mono board > in the system. Why ? A sixteen bit board cannot share a data path with an > 8 bit board. > > Hmmm..... > > Well why can I run Codeview for windows on the mono board with no problems? > > and > > From what I remember B000:0000 has noth'n to do whith A000:0000 and beyond. > (i.e. the VGA memory mapping in VGA mode could care less about the mono > address space.). Barry Simon's article "How to Get the Most From your System's High DOS Memory" in the May 29, 1990 issue of PC Magazine may help clarify the interaction between the VGA and mono cards. He wrote: Finally, there is a general problem (not related to these memory managers) with the high DOS memory area and 16-bit VGA cards. The ISA bus specifications force the bus to run each 128K section of RAM either entirely in 8-bit or entirely in 16-bit mode. So the entire A and B regions must be one type, C and D of possibly a different type, and E and F of the same type. Video 7 makes VGA cards with RAM and ROM capable of 16-bit operation; Paradice comes with 16 bit ROM. When the cards initialize, they look for 8-bit memory and shift to that mode if necessary. This, on my system, my VRAM sees an 8-bit monochrome adaptor at B000h to B100h and shifts all its video RAM to 8 bit, and it seens the SCSI adaptor ROM at C800h to CC00h and shifts the ROM to 8-bit. I'm currently using an Orchid ProDesigner and DFI (Hercules clone) monochrome card with an AMI motherboard. Curiously, benchmarking the system (using PC Mag Benchmarks 5.0 and QAPlus among others) reveals no difference in the VGA performance whether or not the monochrome card is in the system. Sanford Rockowitz Minaret Software BR.SAR@RLG.STANFORD.EDU 415-755-4570