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PostPosted: Wed Jul 18, 2018 11:47 am 
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viewtopic.php?f=2&t=10665&hilit=Gameboy
Remember that? I don't, I just browse old topics. I only joined the forum recently.
Could that be viable?


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PostPosted: Wed Jul 18, 2018 12:18 pm 
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lidnariq wrote:
The problem is that I'm not certain whether it would be sufficiently closer to "emulation" than "porting".

Yeah, porting doesn't have the same cool factor as emulating.

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when the ZX80 is redrawing the screen it's tricked into fetching picture data as though it were executing it, but the hardware shoves a NOP in for the CPU to actually execute.

That's cool! They're just using the CPU to fetch video data from RAM then, there's no actual processing going on? If this is the case, the emulation could be significantly sped up by entirely skipping this part, and in turn the CPU time that's left for running programs will have more time to be emulated. The tile-based display of the ZX-80 also translates really well to the NES, I don't think any tricks will be necessary to implement it.

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Nocash has some excellent documentation: http://problemkaputt.de/zxdocs.htm

Thanks, I'll take a look.

orlaisadog wrote:
http://forums.nesdev.com/viewtopic.php?f=2&t=10665&hilit=Gameboy
Remember that?

Crap, I've literally already asked this in the past! Well, this is a topic that interests me after all. As for the feasibility of emulating a Game Boy (not CGB) on the NES, I think it's doable. If you can display the graphics (NES can do 2bpp grayscale just fine) and more RAM than the original machine (might need bankswitchable WRAM for this one), emulation is possible, even if it's extremely slow.


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PostPosted: Wed Jul 18, 2018 12:21 pm 
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Effective CPU Speed in SLOW mode (when Display is enabled)
For 50Hz Display Refresh: 0.804600 MHz
For 60Hz Display Refresh: 0.536400 MHz

Could the NES possibly emulate that in real time? I doubt it, but hopefully it wouldn't be unplayable.


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PostPosted: Thu Jul 19, 2018 7:30 am 
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Recompilation? That could go at over full speed!
Edit: Wait, is that ZX80/81?


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PostPosted: Thu Jul 19, 2018 8:15 am 
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Gameboy would be really interesting.


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PostPosted: Thu Jul 19, 2018 8:19 am 
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Game Boy allows writing to VRAM in its (fairly long) horizontal blanking period, even without the GBC-exclusive HDMA feature. My only released full scale project for Game Boy, 144p Test Suite, uses hblank fairly heavily for transferring rendered VWF text to VRAM. So I don't see Game Boy emulation at anywhere near full speed being possible without hardware assistance (Wide Boy, RetroVision, or GB-on-an-FPGA).


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PostPosted: Thu Jul 19, 2018 8:50 am 
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I would expect that most games work without this though. If we can predict what it does and when it happens could we replace it with a mapper IRQ in some cases, such as if it's just scrolling?


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PostPosted: Thu Jul 19, 2018 10:05 am 
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IMO, Game Boy wouldn't be anywhere near full speed, period. I'd personal rather work on something that's playable.


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PostPosted: Thu Jul 19, 2018 11:17 am 
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OK.


Why am I posting just to say this?


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PostPosted: Sun Jul 22, 2018 5:13 am 
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tokumaru wrote:
literally already asked this in the past

Literally
tokumaru wrote:
Does anyone have any ideas of other platforms that are relevant enough to be interesting to see emulated?


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PostPosted: Wed Jul 25, 2018 8:56 am 
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I wanted a rom very simple to test in an emuladorde 6502
Without using the memory APU / PPU for and have a weight 8K

https://github.com/mkeller0815/MOUSE2Go ... er/Arduino

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PostPosted: Wed Jul 25, 2018 9:34 am 
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Every one of my ideas got discarded when I reminded myself of the tight vblank period. :lol:

The PC Engine had ports of NES games with game specific PPU/APU emulation code but you can access VRAM at any given time so it's much more capable for the task.

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PostPosted: Wed Jul 25, 2018 10:13 am 
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I would very much like to emulate something on the NES, but not something people will look for 5 seconds out of curiosity and move on, I want to be able to play actual games at a decent speed. The most likely candidates are early home computers with monochrome displays and character-based graphics. I'll keep that in mind for the future, but for now, my time will be better spent on an actual NES game.


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PostPosted: Fri Jul 27, 2018 9:24 pm 
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Does this count?
https://www.youtube.com/watch?v=-hjtfeezAH8
http://www.carlmuellerjr.com/search/lab ... 2F%20I4NES


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PostPosted: Fri Jul 27, 2018 9:54 pm 
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marvelus10 wrote:
Does this count?

That's quite interesting!


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