Testing all video mode - but which ones are graphics ?

R.Wieser

unread,

Feb 13, 2024, 3:08:37 AMFeb 13

to

Hello all,

I've got a small program going thru all video-modi by looping AL from 80
upto FF, calling INT 10, AH=00.

I would like to find out which of those modi are graphical. Ralf Browns
memory list shows 0040:0065 to hold some bits regarding the current video
mode. In my case the lower two bits are of interrest

Mode 03, text, shows the value 01. Alas, mode 0D, graphics, also shows 01.
In fact, only modi 4 thru 6 show a 02 there, and modi 0 and 01 show a 00.
Al others show 01.

And I'm pretty sure there are few other graphics modi above mode 06 ...

tl;dr:
How do I find out if a certain mode is graphics ?

Secondary question : if the lower two bits of 0040:0065 are *not* the
current video-modes graphics and textmode capablities, what do they signify
instead ?

Regards,
Rudy Wieser

JJ

unread,

Feb 13, 2024, 6:23:47 AMFeb 13

to

On Tue, 13 Feb 2024 08:57:32 +0100, R.Wieser wrote:
> Hello all,
>
> I've got a small program going thru all video-modi by looping AL from 80
> upto FF, calling INT 10, AH=00.
>
> I would like to find out which of those modi are graphical. Ralf Browns
> memory list shows 0040:0065 to hold some bits regarding the current video
> mode. In my case the lower two bits are of interrest
>
> Mode 03, text, shows the value 01. Alas, mode 0D, graphics, also shows 01.
> In fact, only modi 4 thru 6 show a 02 there, and modi 0 and 01 show a 00.
> Al others show 01.
>
> And I'm pretty sure there are few other graphics modi above mode 06 ...
>
> tl;dr:
> How do I find out if a certain mode is graphics ?

Easy way: Use BIOS service to read a pixel. It's only applicable in graphic
video mode.

Hard way: Use the video ports to check the current type of video mode. i.e.
graphic or text.

> Secondary question : if the lower two bits of 0040:0065 are *not* the
> current video-modes graphics and textmode capablities, what do they signify
> instead ?

See Ralf Brown's Interrupt List.

R.Wieser

unread,

Feb 13, 2024, 7:56:35 AMFeb 13

to

JJ,

>> How do I find out if a certain mode is graphics ?
>
> Easy way: Use BIOS service to read a pixel.

> *It's only applicable in graphic video mode.*

(bolding mine)

Indeed. And, AFAICT, that means that *you should not be trying to use it*
in a non-graphics mode.

It also says squat about what happens if you do try. Which makes it
useless.

> Hard way: Use the video ports to check the current type of video
> mode. i.e. graphic or text.

And you don't think that suggestion is a bit ... vague ?

>> Secondary question : if the lower two bits of 0040:0065 are *not* the
>> current video-modes graphics and textmode capablities, what do they
>> signify
>> instead ?
>
> See Ralf Brown's Interrupt List.

You're a funny guy. Not.

Whats the matter ? Did you step outof bed with the wrong foot first ? :-(

Regards,
Rudy Wieser

JJ

unread,

Feb 13, 2024, 6:27:08 PMFeb 13

to

Can't give fish all the time. You gotta fish yourself eventually.

R.Wieser

unread,

Feb 14, 2024, 1:57:32 AMFeb 14

to

JJ,

> Can't give fish all the time. You gotta fish yourself eventually.

You know me better than that.

Besides, how do you think I found that 0040:0065 reference ?

But tell me, how come you're assuming that I didn't fish for myself ?

And by the way, nice ignoring me on calling you out on your 'peek a pixel'
suggestion.

Something odd is going on here, and I'm not at all sure anymore that you
really are JJ.

Regards,
Rudy Wieser

wolfgang kern

unread,

Feb 15, 2024, 3:17:22 AMFeb 15

to

On 13/02/2024 08:57, R.Wieser wrote:

> I've got a small program going thru all video-modi by looping AL from 80
> upto FF, calling INT 10, AH=00.

ask again in ALA

R.Wieser

unread,

Feb 15, 2024, 6:17:33 AMFeb 15

to

Wolfgang,

>> I've got a small program going thru all video-modi by looping AL from 80
>> upto FF, calling INT 10, AH=00.
>
> ask again in ALA

alt.lang.ass I presume ? Really ? Half of it seems to be spam. But hey,
I've got little to lose.

Regards,
Rudy Wieser