[zxspectrum] Re: errore 404 ;)
- From: Mario Prato <mario.prato@xxxxxxxx>
- To: zxspectrum@xxxxxxxxxxxxx
- Date: Tue, 20 Jul 2004 13:59:45 +0200
Cioè vuoi dire che lo ZX81 ha già l'hardware necessario per lavorare in
alta risoluzione? Non lo sapevo!
a quanto pare no, hai bisogno di qualche add-on, dalle faq dello ZX81:
Q: Could you get hi-res graphics on a ZX81?
A: Yes. There were a number of ways.
1. The Z80's i register pointed to a font table. You could move this around
in the ROM to create swirly graphics effects. The game Astral Convoy did
this. Unfortunately, the design of the ZX81 made it impossible for the
character set to be anywhere in the 16K range, so you couldn't have a user
defined set without extra hardware. With a 64K RAM pack you could disable
the ROM shadow between 8K and 16K and design your own UDGs.
2. CRL released a Hi-Res graphics toolkit. This contained an extremely
hairy interrupt routine that replaced the ZX81's usual display update
routine. Basically, it pointed the i register to a strategic ROM location,
and tried to 'best fit' the HRG display to what it could find in those
locations. It also used a feature of the ZX81's hardware that allowed you
to have 1 pixel height characters to improve it's chances.
You still could, at best, only have 128 different combinations out of the
256 possible ones. These were the 64 'characters' and their inverses. So
this is really pseudo-HRG.
A number of games by Software Farm, including Hi-Res Invaders and Rocket
Man, used this technique.
With a 64K RAM pack you could also, alter the font, allowing an even better
chance of getting the characters you need. Some people made an alteration
to their ZX81's internal wiring, so that the i register can point to the
16K RAM area, allowing them to do the same.
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