dan@rna.UUCP (Dan Ts'o) (08/22/86)
A question about the ROM BIOS call "set palette", request AH <- 11 of the Video interrupt 0x10. I am trying to write a simple display program that will work on both the CGA and EGA. I am using mode 6 (640x200, 2 color) for this reason. It seems that setting the background color on the CGA actually sets the foreground (pixel on) color, while using "set palette" to set the background in fact does set the background. Is this CGA "feature" suppose to be there ? Cheers, Dan Ts'o Dept. Neurobiology Rockefeller Univ. 1230 York Ave. NY, NY 10021 212-570-7671 ...cmcl2!rna!dan rna!dan@cmcl2.arpa
uchuck@ecsvax.UUCP (Charles Bennett) (10/07/86)
We are currently getting ready to purchase new IBM PC/AT's for the
programming staff here. We utilize the machines in a variety of ways
both for microcomputing and accessing mainframes via async communications
and will be adding an IRMA-X type board for 3279 emulation. We have a
large investment in software, most of which uses color but not
necessarily pure graphics. The question is this; what, if any, are
the incompatablities between the CGA board and the EGA board (with
appropriate monitor, of course). Rumor postulates two completely
different circumstances; 1) CGA software does not run on the EGA, and
2) CGA software runs on the EGA but in CGA mode without special
intervention. ????WHAT IS THE STORY???? !!!!PLEASE!!!!
--
-Chuck Bennett-
919-966-1134
... ...!(decvax|akgua)!mcnc!ecsvax!uchuckben@catnip.UUCP (Bennett Broder) (10/12/86)
In article <2105@ecsvax.UUCP> uchuck@ecsvax.UUCP (Charles Bennett) writes: > >We are currently getting ready to purchase new IBM PC/AT's for the >programming staff here. We utilize the machines in a variety of ways >both for microcomputing and accessing mainframes via async communications >and will be adding an IRMA-X type board for 3279 emulation. We have a >large investment in software, most of which uses color but not >necessarily pure graphics. The question is this; what, if any, are >the incompatablities between the CGA board and the EGA board (with >appropriate monitor, of course). Rumor postulates two completely >different circumstances; 1) CGA software does not run on the EGA, and >2) CGA software runs on the EGA but in CGA mode without special >intervention. ????WHAT IS THE STORY???? !!!!PLEASE!!!! The answer is not so simple. It depends on both the EGA board and the software. The least compatible board you can buy is the IBM. It contains the documented CGA video modes, but not the CGA registers. This means that software that accesses the video board properly (through BIOS calls) will work, but software that attempts to program CGA registers directly will not work. I think you will find about a 70% success rate, slightly worse for games. Some of the clone boards do quite a bit better. The Quadram QEGA+ and similar boards are supplied with ram-resident software that when installed make it possible for most programs that program the CGA directly to work. I have found this works with about 90% of all CGA software. The remaining "trouble" programs are those that are copy protected and must boot from floppy (since the ram-resident software is lost on re-boot), and those that use undocumented CGA modes (like the 16 color mid-res graphics). The most compatible board I have seen is the "vu-tek", which has special soft switches to place the board in CGA emulation, and which supports the undocumented modes. (The emulation is so accurate it even flickers when the screen scrolls!) Since the cga emulation is not lost when you re-boot, even copy protected software runs. The vu-tek runs every piece of CGA software I have ever tried. (I wish I knew about the vu-tek when I bought my QEGA+) In conclusion, I would highly recommend that you opt for EGA boards in your new machines. I consider the text that the CGA produces unacceptable for more than just casual use; I don't think I could program all day on a CGA monitor. If you are concerned about CGA compatibility, be sure to have your dealer test the CGA software you intend to run to see if it will work on the EGA card he is trying to sell you. -- Ben Broder {ihnp4,decvax} !hjuxa!catnip!ben {houxm,topaz}/
bing@galbp.UUCP (Bing Bang) (10/14/86)
In article <> uchuck@ecsvax.UUCP (Charles Bennett) writes: > >We are currently getting ready to purchase new IBM PC/AT's for the >programming staff here. We utilize the machines in a variety of ways >both for microcomputing and accessing mainframes via async communications >and will be adding an IRMA-X type board for 3279 emulation. We have a >large investment in software, most of which uses color but not >necessarily pure graphics. The question is this; what, if any, are >the incompatablities between the CGA board and the EGA board (with >appropriate monitor, of course). Rumor postulates two completely >different circumstances; 1) CGA software does not run on the EGA, and >2) CGA software runs on the EGA but in CGA mode without special >intervention. ????WHAT IS THE STORY???? !!!!PLEASE!!!! >-- > > > -Chuck Bennett- > 919-966-1134 >... ...!(decvax|akgua)!mcnc!ecsvax!uchuck Here's what I have been able to find out on my own. Most EGA cards make atleast a half-hearted attempt to be CGA compatible. Most maker will claim BIOS compatibility, and they achieve this in varying degrees. This means programs that are well behaved, i.e. use the BIOS calls to do everything will most likely run on any good EGA board. However, there are many programs that talk directly to the graphics board and if these programs talk to the EGA board as if it were a CGA board, the result is a scrambled screen. I know of only one EGA card that claims total hardware compatiblity with the CGA (and MDA and hercules and platronics) board. I have it and it works great with all the software I have so far. The board is made by Paradise Inc. called the "Autoswitch EGA". I hope this helps out. --- Bing H. Bang Gun for Hire "Have gun, will travel." ...akgua!galbp!bing
davidsen@steinmetz.UUCP (Davidsen) (10/17/86)
In article <689@galbp.UUCP> bing@galbp.UUCP (Bing Bang) writes: >In article <> uchuck@ecsvax.UUCP (Charles Bennett) writes: >> >>We are currently getting ready to purchase new IBM PC/AT's for the >>programming staff here. We utilize the machines in a variety of ways ... most of which I deleted ... >> The question is this; what, if any, are >>the incompatablities between the CGA board and the EGA board (with >>appropriate monitor, of course). Rumor postulates two completely >>different circumstances; 1) CGA software does not run on the EGA, and >>2) CGA software runs on the EGA but in CGA mode without special >>intervention. ????WHAT IS THE STORY???? !!!!PLEASE!!!! There are two "CGA modes" on the IBM EGA and most compatibles. One is selected by the hardware switches and is close to CGA. The other is selected by a software program (I posted it to net.sources a few months ago) which seems to get complete compatibility. I have yet to find a problem with the IBM board, the Quadram, or the Video7 board. This includes some *very* badly programs. Any hardware/software which switches "automagically" will sooner or later do the wrong thing. -- -bill davidsen seismo!rochester!steinmetz!--\ / \ ihnp4! unirot ------------->---> crdos1!davidsen \ / chinet! ---------------------/ (davidsen@ge-crd.ARPA) "Stupidity, like virtue, is its own reward"