vesa text modes

[ehenkes]

If I switch during bootloading by

Code: Select all

mov ax, 0x4F02
mov bx, 0x010C ; text mode 132*60
int 0x10

into a text mode, how can I use it later in the kernel using PM?
Is there a video RAM like b8000h?

[Combuster]

I'd have read the official (VESA VBE) specification before I would (not) have posted that question

Also, necro alert.

[neon]

This was posted a year ago...

Assuming that the video mode was set to support LFB, you can grab a pointer to its frame buffer (see the specs to find out how.) If not, its probably at 0xa0000 but you will need to provide a way to support switching between banks.

I personally have been using VGA in protected mode as my system is not up to par yet to support VBE to my standards. (I have high standards in design...)

[AJ]

Hi,

I have now split the topic, hence Neon and Combuster's reference to thread necromancy!

Cheers,
Adam

[Tobiking]

I tried it yesterday before ehenkes wrote this. The graphic modes (with lfb) work without problems, but the text modes don't (tested in qemu and bochs). I think ehenkes tried it on real hardware, too. Maybe there is a lack of support for the text modes?

The idea was to find an easy way to extend the normal 80x25 display to be able to put more information on the screen. Using the graphic mode and drawing own fonts seems a bit to much work right now.

[Dex]

You can always use 80x50 as easy as 80x25

[jal]

into a text mode, how can I use it later in the kernel using PM?
Is there a video RAM like b8000h?

If I'm not mistaken, the VESA video mode information structure contains a field indicating the base address for the video mode. Unfortunately, VGABIOS (and thus Bochs) does not support VESA text modes. On a standard VGA, the highest text resolution you can get is 90x60 (720x480 pixels, 8x8 characters).


JAL

[smeezekitty]

i fail to see where 80x25, 80x50 and even 90x60 is not enough for text mode?

[Tobiking]

i fail to see where 80x25, 80x50 and even 90x60 is not enough for text mode?

80x50 is sufficent and it's used for now, but 80x25 wasn't. Printing information about found pci devices takes some space and there is no way to scroll up in the kernel right now.

[ehenkes]

You can always use 80x50 as easy as 80x25

Yes, as Tobiking already mentioned, we have found this possibility and use this 80*50 with 8*8 fonts (a little bit ugly, but helpful) for the time being.

Code: Select all

;;;;; set 80x50 text mode and 8x8 font 	
mov ax, 0x1112 	
xor bl, bl 	
int 0x10 
;;;;;

Could we also expand that resolution to 90*60 in this easy way?

[jal]

Could we also expand that resolution to 90*60 in this easy way?

No, unfortunately not. 90x60 needs reprogramming the VGA controller. It's not that difficult (search the forum, it has come up a few times, with source code), but not as easy as a simple int 10h call.


JAL