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Re: Convert NES into Apple II+

Bryan Parkoff wrote:


    I plan to do the project by remapping NES' ROM and graphic into Apple
II+.  I know that we have already discussed in the past.  It is not very
possible, but there is only one possibility.  Hack by reading NES' ROM and
change the Absolute Address Pointer that points to $2000-$3FFF for high
resolution graphic.  It is what I saw that Apple II+ has only one Super
Mario that is running in high resolution graphic.
    I do understand that NES does not use graphics directly CPU's memory
address, but separate video memory.  I have heard that someone did the
project that allows NES to be running on Apple IIgs.
    I am so curious.  How did NES handle 16 colors on 6502 CPU?  I do know
that it is newer in 1985 rather than 1978.  Is it true that 6502 CPU
manipulate 16 colors into video memory like changing color byte in
$2000-$3FFF.
    Have someone tried to do this project for fun?
I'm not sure which way you're going here; are you trying to run NES software on a II+, or the other way around?
An NES emulator wouldn't be too successful on a II+ without some serious hardware mods. The NES could display 16 colors at a time out of a possible total of around 50; a II+ would only be able to do 6 colors in HGR mode, making the color mappings quite difficult. (Even an Enhanced IIe can only do 16 hard-wired colors in DHGR mode.) Also, the NES had a separate logic unit, a "PPU", that handled all the graphic manipulation and would be impossible to emulate well with just a 6502.
You could probably do it on the IIgs, since it has the video capability to handle it, though emulating the PPU would still be a pain without a faster CPU. 

-lee