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VBE 81ffh in assembly
https://forum.osdev.org/viewtopic.php?f=1&t=33332
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Author:  CheeseBees [ Thu Nov 22, 2018 11:30 am ]
Post subject:  VBE 81ffh in assembly

Can it be used in assembly(im using nasm), and if so how?(in terms of values to set for it)

--EDIT--
can it be used to write to the memory

Author:  Octocontrabass [ Thu Nov 22, 2018 11:44 am ]
Post subject:  Re: VBE 81ffh in assembly

When you say "VBE 81ffh", are you referring to VBE mode 0x81FF?

Why do you want to use it?

What mode is the CPU in when you're trying to use it?

Author:  CheeseBees [ Thu Nov 22, 2018 11:46 am ]
Post subject:  Re: VBE 81ffh in assembly

Octocontrabass wrote:
When you say "VBE 81ffh", are you referring to VBE mode 0x81FF?

Why do you want to use it?

What mode is the CPU in when you're trying to use it?

1. Yes i am
2. To get full access to my video ram as the mode description says its for
3. Real mode

Author:  Octocontrabass [ Thu Nov 22, 2018 12:08 pm ]
Post subject:  Re: VBE 81ffh in assembly

CheeseBees wrote:
2. To get full access to my video ram as the mode description says its for

Why do you want to do that?

CheeseBees wrote:
3. Real mode

You can use this function to get information about the VBE capabilities, this function to get information about the mode you want to use, and this function to set the mode. If VBE 2.0 is supported, you'll probably want to set bit 14 in the mode number (0xC1FF instead of 0x81FF) to use a linear buffer.

I suggest also looking at the VBE specification for the definitions of those functions, since it explains the requirements for calling each, and what the return values mean.

If you're writing a quick proof of concept, you can skip the check for VBE 2.0 since all recent VBE implementations support it.

Author:  CheeseBees [ Thu Nov 22, 2018 12:22 pm ]
Post subject:  Re: VBE 81ffh in assembly

Octocontrabass wrote:
CheeseBees wrote:
2. To get full access to my video ram as the mode description says its for

Why do you want to do that?

CheeseBees wrote:
3. Real mode

You can use this function to get information about the VBE capabilities, this function to get information about the mode you want to use, and this function to set the mode. If VBE 2.0 is supported, you'll probably want to set bit 14 in the mode number (0xC1FF instead of 0x81FF) to use a linear buffer.

I suggest also looking at the VBE specification for the definitions of those functions, since it explains the requirements for calling each, and what the return values mean.

If you're writing a quick proof of concept, you can skip the check for VBE 2.0 since all recent VBE implementations support it.


Thank you so much that just ended 2 years of searching.

Author:  bigboyav [ Sat Dec 29, 2018 3:46 am ]
Post subject:  Re: VBE 81ffh in assembly

Check out the below link, very detailed on how to use VESA Bios Extensions (VBE).

viewtopic.php?f=2&t=30186

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