Question about .nib file regions
So I'm in the process of converting some .nib files to .g64 so they work in VICE, but I noticed a lot of the ones I'm seeing are listed as both (USA, Europe). Maybe I'm mistaken, but didn't these games need to be coded twice for NTSC and PAL timings? Or were these original disks actually region free releases? Thanks
Posted Apr 20, 2017, 4:28 PM UTC
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Timings were different between regions, yes. Even within the NTSC region, the early R56A VIC-II had one fewer cycle per scanline than did later revisions.
It wouldn't matter at all if, for example, a game only used BASIC or Kernal routines. The same binary could work fine on any C64 hardware. If a coder wrote custom interrupt routines then yes, the differences in timing must be considered.
Sometimes a game had different releases for PAL and NTSC regions. But it's also possible to make a binary that uses timing-dependent interrupt routines and works on any C64 system. It's pretty easy to detect NTSC/PAL by using the raster counter. I've never tried to detect R56A VIC-II but I imagine it wouldn't be hard after implementing a stable interrupt. There are many methods but Marko Makela's doc is a pretty good introduction.
So there were many games that were region free? Since so many cracked disks are specifically fixed for PAL, I assumed most commercial games were region coded.
Well, PAL-fixing is the art of disassembling the binary of an NTSC timing-dependent game and re-coding the interrupt routines to work on a PAL system. It's not as if the game studios were necessarily trying to implement region-locking per se but I suppose in many cases that's what you had in effect.
Only an anecdote, but for fun I just tried running three NTSC-region original game disks on my PAL C64. Lode Runner and Leviathan seem to run perfectly. Bubble Bobble seems to run perfectly apart from a scrolling glitch in the Taito splash screen. As could be expected, the games do run at a slower speed and the music tempo and pitch are off. Those are probably two of the most common things to re-code if a studio built unique binaries for the different regions.
I don't know the answer to your question about the number of games that were the exact same in both regions but I suspect it's more than zero!