[Open-graphics] bootstrapping the video mode (outputting VGA text)

[James Richard Tyrer]

Timothy Miller wrote:
> On 8/9/06, James Richard Tyrer <tyrerj at acm.org> wrote:
> 
>>
>> Well that is another issue isn't it.  VGA is based on NTSC.  How is it
>> displayed on PAL?
> 
> Do we care?  We'll just put out a valid PAL mode and use 400 of the
> scanlines (interlaced) for the image.
> 
That will certainly work for the character mode boot.  My comment was a 
bit OT.

But, I was wondering about the general issue.  If a user tries to 
display VGA on a PAL TV set, what happens.  Scan conversion would fix 
the problem but IIUC we aren't going to use hardware scan conversion. 
This would be another advantage of trying to leverage existing hardware.

Obviously, it would be best if the user chose a pixel format (768 x 576) 
that was suitable for PAL display.

I also wonder (I do that and > 90% of the time it goes nowhere, but 
occasionally I come up with something) if PAL TV sets will run at 60 Hz 
vertical field rate?  If so, they would probably be able to display VGA 
since the horizontal (interlaced) scan rates are about the same (15625 
vs. 15750).

-- 
JRT