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PMode and VESA
Posted: Wed Oct 24, 2001 12:01 am
by gedeon
Hello
I started programming my OS few month ago.
And i have now a lot of documentation.
But one question still have no answer
How to programming VESA mode in protected Mode ?
I know how to do that in real mode (int 10 ...), but i have no found documentation for the pmode.
Does anibody have an answer ? or documentation ?
Re: PMode and VESA
Posted: Wed Oct 24, 2001 11:21 am
by Jeroen Jacobs
well... there are two possible solutions :
- Switch to VM86 mode for each vesa-call (not good)
- VESA 2.0 has a 32 bit interface (I think it uses far calls). Search Google for VESA 2.0 . It's very well documented.
Jeroen Jacobs
Re: PMode and VESA
Posted: Thu Oct 25, 2001 11:29 pm
by gedeon
Thank you JJ
It's already done
easiest than google
www.vesa.org
good documentation
Ps : 1st solution, agree with you , very very bad solution beurk!
Re:PMode and VESA
Posted: Fri Apr 26, 2002 12:13 pm
by Pype.Clicker
now, VBE 3.0 is out and supports a full 32 bits API (even for modes enumerating, switching, etc. which had to be done with VM86 with older VBEs)
Oh, by the way, i'm looking for a C implementation of this for my kernel, so if you don't already have a kernel but are already working on the video driver in PMODE, you're my friend
Re:PMode and VESA
Posted: Mon Apr 29, 2002 5:14 am
by gedeon
Thank you i have VBE 3 .0 Documentation.
Sorry but I have a kernel , and for the moment working with VBE mode is not possible with Bochs (maybe it's wrong with 1.4 version), so my OS is in VGA 16 mode.
I work on a website with documentation for my OS and soon it will be online ( i hope), and when my VBE mode driver will be ready , email me and get the source with some explanations.
Re:PMode and VESA
Posted: Mon Apr 29, 2002 5:07 pm
by K.J.
Is VBE 3 supported by many graphics cards?
K.J.
Re:PMode and VESA
Posted: Mon Apr 29, 2002 9:36 pm
by Chris Giese
The protected mode functions supported by VESA 2.x don't
seem very useful. Example: protected-mode bank-switch.
If VESA 2.x has a linear framebuffer, why do you need this?
I could be mistaken, but I thought the VESA 3.x functions
run in 16-bit protected mode.
Re:PMode and VESA
Posted: Tue Apr 30, 2002 12:24 pm
by Pype.Clicker
I could be mistaken, but I thought the VESA 3.x functions
run in 16-bit protected mode.
As far as i remember, yes: you have to jump to a 16-bits code segment, but this is still pmode working, and thus it's really cheaper to implement than if it was in realmode ... It's just a trick bios developers found so that the very same code can be run in both real & protected mode by just changing what differs: segments value (usually, 0xc000 is hardcoded, now you can select 0x28 instead
Actually, i've found VBE 3.0 is present on my GeForce 2, so i guess you can expect it on - say - all video card from Y2K ...