Hi Petruza,
on which system (Windows, LInux, FPGA, PIC, AVR,...) is your emulator running? [...]

Hi, and thanks to everyone for the comprehensive ansers.
I'm developing the emulator core in portable C independent of any platform.
Even the platform dependent code like rendering I'll try to ...

I've finished my cpu emulator, and made some tests on it and I can say it's fairly complete and ready to be used on a host system development.
Which system would you say is simpler and easier to emulate? (e.g. Atari VCS, Atari 8-bit, Apple II, C64, NES, BBC Micro, etc. )
I don't want to do a 100 ...

It's OK since the NES has no decimal mode and my first goal for the 6502 emu is to be used in a NES emu so I'm OK with no decimal
will try it, thanks

I'd go with Ian Piumarta's run6502, because it's C and command-line. It is quite compact and quite clever C, so it may be a learning experience.
http://www.piumarta.com/software/lib6502/
Thanks Ed for the suggestion, I'm debugging it to try and understand how to call a single instruction so I run ...

(pedantic note: what you are talking about is a simulator , not an emulator
Not pedantic at all, it's good to learn the right terminology. I come from a more software-oriented view of emulation were we call them emulators as in MAME, but reading this site and forum I see here that simulator makes ...

1) I've seen some but they I didn't find any with a clear documentation of how to run it and how to know the test results. Anyway, I could run tests, or games or whatever piece of machine code. The important thing is comparing if the outputs are different or the same.
2) Good advice, I'll try that ...

Hi Ryan, although I'm more into emulator development rather than 6502 programming, your idea of modifying existing games interested me because that's mainly the same idea I had that made me start writing my own emulator, so I'd like to hear about the progress of you project here.

I guess you want ...

Hi, I'm writing a 6502 emulator, I'm testing it with a ROM I'm doing myself too, but would like to have some other emulator to compare to, as a reference.
As when I see my emu doing something different than the other emu, it will point most likely to a bug in mine.

For that, I need an emulator that ...