Image Map Image Map
Page 1 of 22 1234511 ... LastLast
Results 1 to 10 of 217

Thread: True CGA vs VGA card in CGA mode

  1. #1

    Default True CGA vs VGA card in CGA mode

    Hi all

    Is there any performance differences between a true CGA card and a 8-bit VGA card running CGA graphics ?

  2. #2

    Default

    If it has switches so it oculd be toggeled to CGA mode on startup, it would operate as a CGA, and there would be no differences unless the card is of lower quality and price.

    However, if it's configured as VGA on startup, it might have some problems with certain CGA graphics modes.

  3. #3
    Join Date
    Apr 2005
    Location
    Stevens Point, Wisconsin
    Posts
    2,315

    Default memory map

    Well, they typically live at different addresses in the pc's address space.
    0A0000-0AFFFF VGA/EGA Video Memory
    0B0000-0B0FFF Monochrome Video Memory
    0B8000-0BFFFF CGA

    patscc

  4. #4

    Default

    Quote Originally Posted by patscc View Post
    Well, they typically live at different addresses in the pc's address space.
    0A0000-0AFFFF VGA/EGA Video Memory
    0B0000-0B0FFF Monochrome Video Memory
    0B8000-0BFFFF CGA

    patscc
    Okay. I was thinking more along the line: If I run a game in CGA on a VGA card or run it on a true CGA card, will there be any noticeable performance differences ?

    I talk simple games, like Alley Cat

  5. #5

    Default

    Quote Originally Posted by QuantumII View Post
    Okay. I was thinking more along the line: If I run a game in CGA on a VGA card or run it on a true CGA card, will there be any noticeable performance differences ?

    I talk simple games, like Alley Cat
    I have had some problems with that. Often, the VGA is toggeled into wrong video modes, ant it doesn't really support some of the special modes of the CGA, like some of the CGA's graphics mode, like morecolors and the BG/red/cyan/white palette.

    See the attachement of running Flightsimulator 2.13 (Booter) on a VGA in VGA mode and VGA in CGA mode. Note that "Signal Error" alert in the upper right courner on one of the pictures, hence, NOT recomended on CRT monitors.
    Last edited by per; April 28th, 2009 at 05:10 AM.

  6. #6

    Default

    Quote Originally Posted by per View Post
    I have had some problems with that. Often, the VGA is toggeled into wrong video modes, ant it doesn't really support some of the special modes of the CGA, like some of the CGA's graphics mode, like morecolors and the BG/red/cyan/white palette.

    See the attachement of running Flightsimulator 2.13 (Booter) on a VGA in VGA mode and VGA in CGA mode. Note that "Signal Error" alert in the upper right courner on one of the pictures, hence, NOT recomended on CRT monitors.
    Galaxian is one game I know that does this. It works on some VGA monitors, but on others the picture loses sync.

    Moon Patrol always locks up about 7 seconds into the game (Demonlord noted this on his site). Both of these games have some kind of problem with VGA, but I'm not sure what.

    VGA is BIOS compatible with CGA, but not register compatible. At least 60% of CGA software works on VGA, but the other 30% either partially or completely fails. This can be caused by any of the following:

    *Setting video modes or color palettes by writing directly to the registers

    *Using the 160x100 pseudographics mode

    *Raster interrupts

    *Tweaking the 6845 registers to produce effects like screen shaking

  7. #7

    Default

    Quote Originally Posted by per View Post
    I have had some problems with that. Often, the VGA is toggeled into wrong video modes, ant it doesn't really support some of the special modes of the CGA, like some of the CGA's graphics mode, like morecolors and the BG/red/cyan/white palette.

    See the attachement of running Flightsimulator 2.13 (Booter) on a VGA in VGA mode and VGA in CGA mode. Note that "Signal Error" alert in the upper right courner on one of the pictures, hence, NOT recomended on CRT monitors.
    Yeah, I tried FS on VGA, and it was just like your picture.. Say, did you boot the game from a floppy or did you run the fs.com file ?

  8. #8

    Default

    Quote Originally Posted by QuantumII View Post
    Yeah, I tried FS on VGA, and it was just like your picture.. Say, did you boot the game from a floppy or did you run the fs.com file ?
    I booted from a floppy (from retrogade, that one got no hidden message on it).

    You say you got a CGA with a RCA jack. If you got a monitor/TV capable of displaying NTSC, you could connect it to the CGA. FS is a lot better in composite than RGBI.

  9. #9
    Join Date
    Jan 2007
    Location
    Pacific Northwest, USA
    Posts
    28,869
    Blog Entries
    20

    Default

    How about a CGA with a scan converter box (as discussed on other threads?). I assume the idea is to use a VGA monitor.

  10. #10

    Default

    Quote Originally Posted by Chuck(G) View Post
    How about a CGA with a scan converter box (as discussed on other threads?). I assume the idea is to use a VGA monitor.
    Yes, if I cannot get a CGA monitor within reasonable time (I'm an impatient guy sometimes) I'll get one of those.. They could be nice to have anyway
    Current machines:
    PCs: IBM PC XT 640K, IBM PC XT 256K ,IBM PC XT , 2x IBM PC AT, Compaq Portable I, Compaq Portable II, Compaq Portable I/286, Philips Logic Analyzer XT clone, IBM PS/2 Model 30 286 , HP 95X, HP200LX (2x),Compaq SLT/286.
    Apple: Macintosh 512k, Macintosh SE, Macintosh Classic, PowerBook 170, iBook Clamshell, iBook G3,iMac G4 , TiBook's, Apple IIc, Many newer machines (G4, G5, Intel..), 20th Anniversary Mac
    Others: Commodore 64C,Amiga A500, CCS S-100 System, SNES,

    Wanted: Macintosh 128k, Hard Disk 20, System disks and games for the Mac

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •