Re: Now that the source of "Prince of Persia" is out there...

[BLuRry <brendan.robert@gmail.com>]

On Thursday, April 26, 2012 11:16:09 AM UTC-5, Vladimir Ivanov wrote:
> On Thu, 26 Apr 2012, BLuRry wrote:
> 
> > On Thursday, April 26, 2012 10:02:31 AM UTC-5, Vladimir Ivanov wrote:
> 
> >> How about the messy //c VBL?
> >
> > Yes, it also has //c VBL.  In fact, you can read Jordan bitch about 
> > discovering bugs in it if you read his dev journal. :-D
> 
> Found it, thanks. Was just wondering how many later games had to support 
> all three VBL modes and were there any early //e-only that gave problems 
> on //c and IIgs.

Not sure, really.  I know that the HBL behavior of the floating bus changed from the ][/][+ to the //e,c,gs models.  So anything based on the original Apple ][ behavior will certainly not work correctly.  Still, I believe that most incompatibilities will be due to older programs' use of invalid/undocumented 6502 opcodes.  65C02 processors either reassigned those or NOP'd them.  Hopefully the list is rather short, I don't remember many things breaking when I was a kid.

-B