Date   : Fri, 02 Dec 2016 10:46:45 +0000
From   : nicolagiacobbe@... (nicola giacobbe)
Subject: Updated BeebWiki articles

Thanks Rob, the discussion is catching but from it seems that I am asking
too much to the Beeb

. BTW the demo is impressive, really; I would very like to be able to write
such code.


________________________________
From: bbc-micro-bounces+nicolagiacobbe=hotmail.com@...
<bbc-micro-bounces+nicolagiacobbe=hotmail.com@...> on behalf
of Rob Coleman <rgcolem.myorg@...>
Sent: Friday, December 2, 2016 9:05 AM
To: bbc-micro@...
Subject: Re: [BBC-Micro] Updated BeebWiki articles

On 02/12/2016 07:37, Nicola Giacobbe wrote:
> By the way and asking to all the experts out there: is there some way to
> reduce the vertical resolution of a MODE while keeping it screen-height?
> I mean, I have found many references to reducing the number of rows on a
> graphics mode but the final result is that I end using only a part of
> the available screen area. Something akin to a 256x128 MODE 5 could be
> very useful.
> Any ideas?
I don't think a full screen 256x128 mode 5 is possible due to the way that
the CRTC automatically increments the row counter.

I haven't tried this but it is possible to display the first scan line in a
row over and over again. You set the CRTC to display one scan line per
character in R9 and then use the vertical rupture technique to change the
screen start address on every scan line.

The problem with this is that you're only using 1/8th of the available
screen memory so you quickly run out unless you drastically reduce the
vertical resolution. A 256 x 32 pixel MODE 1 would still take up 16K. On a
Master, using shadow RAM and all of the screen memory (40KB), you could get
up to 256 x 80.  You could use even more main memory to increase the
resolution further but it would make hardware scrolling difficult (if not
impossible - I haven't thought through the details).

There's a brief discussion about this technique (and a link to a demo that
implements it) on the RetroSoftware boards:
http://www.retrosoftware.co.uk/forum/viewtopic.php?f=3&t=122


_______________________________________________
bbc-micro mailing list
bbc-micro@...
http://lists.cloud9.co.uk/mailman/listinfo/bbc-micro
bbc-micro Info Page - lists.cloud9.co.uk<http://lists.cloud9.co.uk/mailman/listinfo/bbc-micro>
lists.cloud9.co.uk
Your email address: Your name (optional): You may enter a privacy password
below. This provides only mild security, but should prevent others from messing
with ...