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 Post subject: VBE 81ffh in assembly
PostPosted: Thu Nov 22, 2018 11:30 am 
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Joined: Mon Nov 19, 2018 12:13 pm
Posts: 22
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

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- Mitchell Barnes the Confused Idiot
17 years old and programming assembly

“If you're going to tell me to give up then you're wasting time that you could be using to help someone else”

“Assembly is more readable and easy to use than c. Change my mind”


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 Post subject: Re: VBE 81ffh in assembly
PostPosted: Thu Nov 22, 2018 11:44 am 
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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?


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 Post subject: Re: VBE 81ffh in assembly
PostPosted: Thu Nov 22, 2018 11:46 am 
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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

_________________
- Mitchell Barnes the Confused Idiot
17 years old and programming assembly

“If you're going to tell me to give up then you're wasting time that you could be using to help someone else”

“Assembly is more readable and easy to use than c. Change my mind”


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 Post subject: Re: VBE 81ffh in assembly
PostPosted: Thu Nov 22, 2018 12:08 pm 
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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.


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 Post subject: Re: VBE 81ffh in assembly
PostPosted: Thu Nov 22, 2018 12:22 pm 
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Joined: Mon Nov 19, 2018 12:13 pm
Posts: 22
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.

_________________
- Mitchell Barnes the Confused Idiot
17 years old and programming assembly

“If you're going to tell me to give up then you're wasting time that you could be using to help someone else”

“Assembly is more readable and easy to use than c. Change my mind”


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 Profile  
 
 Post subject: Re: VBE 81ffh in assembly
PostPosted: Sat Dec 29, 2018 3:46 am 
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Joined: Sat Dec 29, 2018 3:09 am
Posts: 10
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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