kolla wrote: ↑Wed Feb 17, 2021 11:09 am
Just C:Date, like you
I have done some simple tests now, and it really seems to be related to screenmodes!
Well that does make sense, since the CIAs' Time-of-Day counters are edge-triggered by video signals. (One CIA counts HSyncs, the other counts VSyncs.)
* PAL modes - system time is mostly correct, and if anything, just a wee little slow
* NTSC and RTG modes - system time is 8-10 secs too fast per minute
OK great - useful information. I must admit I didn't test from MiST last night, I used my devboard instead - but that shouldn't (!) make any difference.
I also only tested with my old WB3.0 installation from the A4K days - I'll test again with 3.1.4 and see if that makes any difference.
[Edit: yes, it does - system time gains time if the VBlank frequency is higher than 50Hz under Kickstart 3.1.4, but not under Kickstart 3.1 - even using the same installation - so it seems to be a ROM thing. Does that match what you see?]
I found a fun way to confirm the above... if I use AmiTimeKeeper (an NTP client) and tell it to correct time from NTP every 60 seconds, the correction is for example 9825360 microseconds (close to 10 seconds) when RTG screen is foremost, but only 152587 microseconds (close to 0 seconds) when PAL screen is foremost
Well that just raises more questions - like how are you contacting an NTP server from MiST?!