Interesting developments. Last week I ran SysInfo on my 500+ to see if it rated the 50MHz Derringer at the right speed (rates it 51MHz, FWIW.) I noticed that it determined the system was PAL. Odd... I don't think anything of it because for many years it was working fine as an NTSC system, right?
Well, the signs make sense now. For instance, many games and demos I run on my REAL NTSC systems (2000, 1200, 4000) always seemed to have different timing, along as some music. Nah.
Tonight I'm having a peek around the custom chips area of the Big Book of Amiga Hardware and I think about the 2MB Agnus. There it seems that there were two version of the 2MB 8275 Agnus used in the 500+, PAL (-01) and NTSC (-02). Hmmmm, you thinking what I'm thinking?
I crack the hood tonight and, yup, my 500+ has a PAL chip in it. Has always worked seemingly fine under NTSC, but my memory says to me that I never ran an OS older than 3.1 on this system, so NTSC monitor driver only. Does that make sense?
But it's definitely running PAL -- I have it connected to my FP2001 LCD monitor which shows "PAL@50Hz" in the early startup menu. Well, I'll be darned.