On Sun, Jan 12, 2003 at 12:39:29PM +0000, Andrew Collier wrote: > On Sunday, January 12, 2003, at 10:48 am, Stuart Brady wrote:
> >Presumably a good deal of work would be needed to slow the game back > >down to its original speed, after the framerate had been increased? > > As far as I know, they didn't bother. Although, because of RAM > contention, the running speed of the Sam in Mode 1 is not all that > faster than the Spectrum. I wan't clear - I meant to refer to the speedup that would have been obtained had they decided to use Mode 2 instead of Mode 1. > >Yes, the SAM and Spectrum 128k do provide page flipping. If I remember > >correctly, you are limited to just two pages on the Spectrum 128k, but > >but on the SAM, any page in main memory may be used. I've not actually > >tried using page 31 in modes 3 and 4 yet, but I expect that this uses > >page 0 for the upper 8k of the video memory. > > A mode 3 or 4 screen always starts on an even numbered page. If you > output 31 (and mode bits) to the VMPR than you'll get a screen starting > at page 30. Ouch. If bit 6 of the VMPR is set, bit 0 is taken as 0? I see now that Version 3.0 of the tech manual makes note of this, but it's not quite as clear as it could have been. Thanks for telling me. > >I also wonder whether the extra memory would be of particular benefit. > > Yes, at least if you're drawing in Mode 4. Do you remember a demo > called DWC (Dead Wild Cat) by Marc Broster on Fred 50? It drew rotating > 3D wireframe objects and usually kept up to 50 fps. He used most of the > Sam's memory to hold pre-calculated line drawing routines. I will certainly take a look at this some time soon. Thanks. -- Stuart Brady
