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Game Gear LCD Scaling

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The Game Gear's hardware is very similar indeed to the Master System's - so similar that you can play Master System games on a Game Gear via a special adapter. Some Game Gear games were just the Master System ROMs in a Game Gear cartridge. [smile]

That said, the Game Gear's LCD is only 160x144, and the Master System has a resolution of 256x192 (or 256x224 or 256x240, but those modes were very rarely used). In Game Gear mode, this resolution is simply cropped. In Master System mode something more interesting has to be done to scale this down to fit the LCD.

I won't bore you with the details here, but will refer you to a post here on the subject. Using the research, I added a mode to the VDP emulator that would mimic this scaling.





This is old news, of course. I have nothing especially new to report, but I have pretty much entirely rewritten the emulator now (apart from the Z80 emulator, which was fairly well designed). The code was absolutely horrible, and so I've redesigned it to be a lot more flexible and intuitive to use as a library. I've rewritten the standard memory mapper, I/O mapping, and VDP (though I did copy the rasterisation and timing stuff from the old VDP code and cleaned it a little); there's a lot more to do (so far I haven't even reintroduced joypad input) but at least it'll be nicer for me to work with. [smile]

In the meantime, here are some ugly screenshots of what Master System games look like on the Game Gear LCD.







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It's interesting that those resolutions are the exact same as the GameBoy and NES.

I was going to say something about who would play those ugly/blurry games, but then I remembered owning a GameBoy.

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Original post by Scet
It's interesting that those resolutions are the exact same as the GameBoy and NES.
Interesting information indeed. [smile] I was unaware of that!

The extended resolutions (256×224 and 256×240) were only available on the Master System 2 hardware, limiting their usefulness. 256×240 was especially useless - with that much active display the NTSC VDP couldn't generate vertical blanking signals.

The Master System VDP was based on a TMS9918 (as found in the MSX), which would be where it inherits the standard 256×192 resolution from. It also appears to inherit some bugs - the TMS9918 only supports four sprites per scanline. The Master System VDP supports eight, but if you try to use eight zoomed sprites on a scanline, only the first four are correctly zoomed (this was fixed in the Master System 2 VDP).

I never knew what the Game Boy's LCD resolution was, but always assumed it was higher than the Game Gear's given how crisp it looks in comparison.

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