On Sunday, January 12, 2003, at 10:48 am, Stuart Brady wrote:
On Sun, Jan 12, 2003 at 01:46:52AM +0100, Thomas Harte wrote:
Did they use exactly the same file on the disk, just adding a BASIC
program to switch into mode 1? If so, the SAM 'version' couldn't have
taken longer than 5-10 minutes work, surely!
I think they also hacked the load/save routines so that they used Sam
disks instead of the tape. 7-12 minutes then.
This begs the question; how
much did each version cost?
More than the Spectrum version ever did! (About 15 pounds, if I
remember correctly).
- mode 1 display, with obvious effects on running speed
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.
- software double buffering, even though in the SAM (and 128kb
Spectrum, I believe)
this can be achieved in hardware
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.
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.
Andrew
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--- Andrew Collier ----
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