BigDigg

It's definitely weird but it only happens when launching from BigBox mode and is repeatable. I don't recall this happening before the most recent LB update but then I'm a bit new to this and haven't spent much time on the SNES emulators. Performance is flawless on Retroarch launching different ways and like you said the PC should be plenty powerful enough to manage this.

I'm having the same problem so wonder if there's something more to this. Slowdown (for me) seems limited to snes9x core in Retroarch and only when launched by BigBox. Games play 60fps when running Retroarch direct or launched from Launchbox (vs. BigBox). Interestingly it seems to run OK the first time I run it following a fresh reboot but subsequent snes9x launches lose 5-10fps with stutter and audio issues. I've checked that closing retroarch and bigbox don't have any zombie processes but still persists after closing and relaunching. My PC is a KabyLake i37100 with 16gb ram on Win10 64bit. Thoughts? I'll play around with others to see if it's limited to snes9x core...