DOS ain't dead - How to detect the text mode?

How to detect the text mode? (Developers)

posted by Japheth , Germany (South), 15.11.2020, 17:13

> Howto detect text-mode segment 0xB000 ? (instead 0xB800)
> This is case for MDA and Hercules (not sure).
> Is it enough - 0040:0065 bit 3 ? (2 in RBIL notation)

Checking BIOS variables is ok in most cases. Usually if word at 40h:63h is 3D4h, it's meant a "color" mode starting at 0B800h, and 3B4h means "monochrome" mode at 0B000h

What's more fun is to check the graphics controller, "miscellaneous" register 6, bits 2-3:

3 2 Addressing Assignment 0 0 A0000 for 128KB 0 1 A0000 for 64KB 1 0 B0000 for 32 KB 1 1 B8000 for 32 KB

So you can even set your text mode buffer to A000, size 128 KB. However, I'm not sure if all VGA-compatible cards will accept this.

http://www.o3one.org/hwdocs/vga/vga_app.html

---
MS-DOS forever!

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Complete thread:

How to detect the text mode? - Laaca, 14.11.2020, 11:00 (Developers)
- How to detect the text mode? - Japheth, 14.11.2020, 16:01
  - How to detect the text mode? - tkchia, 15.11.2020, 08:01
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- How to detect the text mode? - DosWorld, 15.11.2020, 15:12
  - How to detect the text mode? - Japheth, 15.11.2020, 17:13
    - How to detect the text mode? - DosWorld, 15.11.2020, 18:49
- How to detect the text mode? - bretjohn, 31.12.2020, 17:52