On Wed, May 21, 2008 at 03:16:07PM +0100, Thomas Harte wrote: > If you interrupt routine is small, could you not also just switch off > the first one or two scanlines of your display, and even grab a few > extra cycles out as a result? Or can you not enable and disable the > display per scanline?
Hi, You could, yes. You can alter pretty much anything about the screen on a line-by-line basis - and if you're very careful, during those lines in the screen area itself! For example, MMENOdemo 1 part 2 (on Fred 60) changes the screen page during the raster; repeatedly switching between foreground and background screens to draw lit and unlit rectabgles - which togehter form a scrolling message. Various other programs switch between mode 4 and mode 3, to get high resolution in a certain area of the screen - Edwin Blink's menu on Blitz (issue 6, was it?) and David Laundon's Fred menu come to mind. Anyway - in this particular case I wanted to display the whole screen; and in the case of one or two scanlines, it probably takes longer to set up the line interrupt handling, than you save by having the screen turned off. Cheers, Andrew -- --- Andrew Collier ---- ---- http://www.intensity.org.uk/ --- -- r<2+ T<4* cSEL dMS hEn/CB<BL A4 S+*<++ C$++L/mP W- a-- Vh+seT+ (Cantab) 1.1.4
