Re: Writing emulator...

[steve@dosius.zzn.com (Dosius)]

Holger Picker <pickerh@uni-muenster.de> wrote in message news:<Pine.A41.4.44.0209090930400.222564-100000@zivunix.uni-muenster.de>...
> a) About the language card: I may be wrong, but in your code the readbank
> and writebank functions differ in that way that when calling writebank you
> do not subtract 0xd000 from addr, neither is that done within writebank. The
> index you've got then might be wrong. (You also check for addr<4096, which
> may not work then.) 
Ouch.  You are so right, I've got a case of PEBKAC (probable error is
between keyboard and chair)...or PBD (programmer is braindead) :E

> [...] later
> AppleIIes (and, of course, the AppleIIc) were shipped with 65c02 processors
> that do not have illegal instructions anymore, just NOPs. In other words:
> You can almost ignore them, as long as you make sure that you skip the right
> amount of bytes that belong to the instruction. BTW.: This is a bug in
> AppleWin, and I know of one case where, as a result, a disk image does not
> work with AppleWin. (Oh dear, I should write a mail to Oliver about it...)
M65C02 nops invalid opcodes.

> d) Could I ask you, please, whether your C-compiler generates 16-bit real mode
> code or 32-bit protected mode code? This is important if you want a good
> emulation of the various AppleII resolutions. You can stick to DOS, of
> course, if you like (my first PC emulator also runs under DOS), but 16 bit
> real mode today is simply a dead end and far too slow.
Fast enough on my 1996-era PC... not as fast as I'd like though but I
don't think going to gcc will help much.