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Thread: Graphics Card and DOS

  1. #1

    Default Graphics Card and DOS

    I just replaced the graphics card in a Pentium 1 machine that is running DOS 6.21. The original was 2MB, the replacement is 4MB. Is there a way to check and see if the 4MB is recognized by the OS? Please keep in mind that I am new to DOS.

    Thanks

  2. #2
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    DOS won't notice the extra RAM on the video card. Running Windows or another GUI capable of high color modes would show if it works.

    Maybe MSD would tell what the card reports for memory. I don't remember which diagnostic tools for DOS recognized large amounts of memory on a video card.

  3. #3

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    I see, so is there a maximum amount of video RAM that DOS recognizes. My 486 has 1MB of on-board video ram, I was thinking of adding a ISA graphics card but maybe I'll just leave it as-is.

  4. #4

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    DOS doesn't specifically care about the video RAM as it is text only. Graphical DOS software (particularly games) make use of extra video RAM for higher resolution video modes. Older video cards (MDA and CGA) had set amounts of video RAM (usually 4KB and 16KB respectively). EGA and VGA cards could have up to 256KB of video RAM. VESA Super VGA cards could have additional video RAM (generally up to 4MB in the DOS era). More video RAM means higher video resolution support.

    Examples:
    640x480 8-bit color requires 307,200 bytes (300KB)
    640x480 15-bit or 16-bit color requires 614,400 bytes (600KB)
    640x480 24-bit or 32-bit color requires 1,228,800 bytes (1.2MB)
    1024x768 8-bit color requires 786,432 bytes (768KB)
    1024x768 15-bit or 16-bit color requires 1,572,864 bytes (1.5MB)
    1024x768 24-bit or 32-bit color requires 3,145,728 bytes (3MB) - this is generally the highest resolution any DOS program will ever use

    Use VESA BIOS function INT 10h/4F00h to determine if VESA is supported and how much video RAM is present.

  5. #5
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    If your system has an official Diagnostics utilities set, that might tell you. But otherwise pcdosretro has the goods.

  6. #6

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    Quote Originally Posted by pcdosretro View Post
    DOS doesn't specifically care about the video RAM as it is text only.
    I see. The machine will be used for AutoCAD 3D modeling so I guess that's where the amount of video ram is important.

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    For most DOS programs, it isn't the amount of video RAM that is important, but how fast it is. Most AutoCAD drivers are going to render using software, so a fast host computer and a fast video card are more important than whether the card has 2MB or 4MB of RAM.

    That said, I would consider 1MB of RAM the minimum, so that you can use AutoCAD in 1024x768 in 256 colors, or 800x600 in 15- or 16-bit color.

    Some cards had minor amounts of acceleration, and there were drivers for AutoCAD that supported that acceleration. You'd have to do research (old InfoWorld magazines? AutoCAD manual and README files?) to figure out which ones.
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  8. #8

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    Thanks. I have not considered speed, will have to dig a little deeper.

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    I've attached the AutoCAD R12 for DOS driver disk readme file, which lists some cards with mild acceleration or enhanced color support. They also support any card with VESA.

    autocad_R12_dos_readme_drivers.txt
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  10. #10
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    Quote Originally Posted by acad_2k View Post
    I see, so is there a maximum amount of video RAM that DOS recognizes. My 486 has 1MB of on-board video ram, I was thinking of adding a ISA graphics card but maybe I'll just leave it as-is.
    What is the graphics chip set? On some onboard graphics you can add extra memory for a greater resolution.
    Thomas Byers (DRI)- "You'll have a million people using the A> [MS-DOS prompt] forever. You'll have five million using [nongraphic] menu systems such as Topview, Concurrent PC-DOS, Desq, and those types. But there'll be 50 to 100 million using the iconic-based interfaces."

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