Date   : Thu, 05 Mar 2009 11:28:47 +1100
From   : richard@... (Richard Wilson)
Subject: Fwd: New Screen Modes with ARM7 Co-Processor?

 

> -----Original Message-----
> From: John Kortink
> Sent: Thursday, 5 March 2009 10:07 AM
> To: bbc-micro@...
> Subject: Re: [BBC-Micro] Fwd: New Screen Modes with ARM7 Co-Processor?
> 
> 
> >> That's not how it works.
> >> 
> >> The length of the vsync and display periods are always
> >> exactly the same.
> >
> >Perhaps you should actually write some code to test this
> >instead of just assuming [...]
> 
> I have, and the result is exactly 20000 1 MHz ticks
> between vsyncs, minus 2 occasionally.
> 
> So, apparently, I'm not the one making assumptions.
> 

Sorry John, you are correct. Somehow the 6845 inserts an extra scan line
into the even frames, or delays the VSYNC for a whole scan line.

Richard