MSX Emulators having built-in debugger

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Por Guillian

Prophet (3455)

imagem de Guillian

10-04-2003, 16:26

He shouldn't need FM/SCC chips. Both chips are already being reverse engineered very heavily. The SCC implementation in openMSX is currently the most accurate one, I think. And as for FM, the YM2413 emulation in MAME sounds remarkably correct. Both applications are open-source, so it would be a shame to duplicate these efforts...

Yep, that is a good reason. But since NO$MSX is full-coded in assembler, he is not interested in C/C++ rutines. That is why he need the real hardware.

Anyway, I know he don't need to reinvent the wheel, and would be better to join efforts for making a better emulator. But since it is a hobby, and he don't want to compete for "the best MSX emulator", you will understand him.

About SCC implementation in openMSX. I think I can cheat it easily with a SCC detection rutine Wink
(of course I agree it is the most acurate one)

Por anonymous

incognito ergo sum (116)

imagem de anonymous

10-04-2003, 16:47

Yep, that is a good reason. But since NO$MSX is full-coded in assembler, he is not interested in C/C++ rutines. That is why he need the real hardware.He should be interested in the C/C++ routines, because they describe the algorithm he needs to implement in assembler. In other words, in stead of translating documentation to assembler and find out all the details by himself, he can just translate the available C/C++ routines to assembler.

But since it is a hobby, and he don't want to compete for "the best MSX emulator", you will understand him.Yeah Smile

About SCC implementation in openMSX. I think I can cheat it easily with a SCC detection rutine WinkPlease try! I'm sure the developers will appreciate that, because afterall, openMSX aims for perfection.

Por Guillian

Prophet (3455)

imagem de Guillian

10-04-2003, 17:02

Please try! I'm sure the developers will appreciate that, because afterall, openMSX aims for perfection.

Ok! I will try to find some free time and do it. Where should I send it?

Por anonymous

incognito ergo sum (116)

imagem de anonymous

10-04-2003, 17:27

>>
About SCC implementation in openMSX. I think I can cheat it easily with a SCC detection rutine Wink

I think that a SCC implementation is not better if it can be cheated or not.
After all, I'm not sure that SCC chip was designed for being detected (at least in a strange or tricky way).

Anyway, as GuyveR800 said, the developers will appreciate any thing helping to accurate the emulation.

Por Guillian

Prophet (3455)

imagem de Guillian

10-04-2003, 17:47


I think that a SCC implementation is not better if it can be cheated or not.
After all, I'm not sure that SCC chip was designed for being detected (at least in a strange or tricky way).

The point is to implement all SCC registers, and try to emulate the real hardware as close as possible. If I can cheat it, using SCC registers or real hardware behaviour, that would mean the implementations is not "perfect", that is what openMSX is aiming for.
Of course the "tricks" I will use are not really important, since they are not used in any Konami game.

Por anonymous

incognito ergo sum (116)

imagem de anonymous

10-04-2003, 18:36

>>
Of course the "tricks" I will use are not really important, since they are not used in any Konami game.

That's the point Smile

Por Guillian

Prophet (3455)

imagem de Guillian

10-04-2003, 18:52

You mean that if Konami doesn't use it in their games, it is not a worth thing?
So SCC specifications is what Konami uses, not what SCC can do (?!)
Then SCC can not be used in demos/games out of "official" especifications?
I don't think so.

Por anonymous

incognito ergo sum (116)

imagem de anonymous

10-04-2003, 19:15

A good example of this is the 'test' or 'deformation' register that is present on both SCC and SCC+ (albeit in different locations). Konami does not use it at all, but it's interesting nevertheless.
Also, the Z80 and the VDP are also used out-of-spec in some games/programs. Should emulators declare these softwares incompatible? I think not.

Por anonymous

incognito ergo sum (116)

imagem de anonymous

10-04-2003, 20:24


Also, the Z80 and the VDP are also used out-of-spec in some games/programs. Should emulators declare these softwares incompatible? I think not.

Well, in this case let's say 'compatibility is not 100% guaranteed' which doesn't mean necessarily 'incompatible'. Smile

Anyway I remember that R800 was said to be 100% Z80 compatible. Nevertheless there are some undocumented Z80 instructions not working fine on R800 (AFAIK).

I think that using undocumented features implies a (minimal) risk. When developing, you may accept that risk or may not. Many people do accept it (including software houses). I have written some pieces of code using 'incompatible' features as well.

But my humble opinion is that I cannot guarantee compatibility if I use undocumented features.

Maybe this is a good issue to be continued in another thread.
(The initial thread was about debuggers, do you remember?) Tongue

Por anonymous

incognito ergo sum (116)

imagem de anonymous

10-04-2003, 20:53


Then SCC can not be used in demos/games out of "official" especifications?

I didn't say that Smile

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