Famicom Disk System unreasonably slow compared to NES on the same core???

[cacotigon]

Had a hankering for a chunk of cheese but mainly the Japanese version of the Lost Levels on the Famicom Disk System. I use the lr-fceumm core with my NES with the following settings to reduce input latency:

video_driver = "dispmanx"
video_threaded = "false"
video_frame_delay = 4
video_max_swapchain_images = 2

Combined with TV Game Mode it works super well and I can play almost as well as I can play on a CRT with an original NES system.

I initially used the default nestopia core for my FDS, but from some marginal testing it seems to be much more CPU intensive than the FCEU core. I'm not able to use any of the aforementioned settings which means the input latency is so bad it feels like Mario is wearing shoes with a gallon of bubbletape gum stuck to them. Unfortunately the FCEU core with the famicom disk system is better but even then it suffers from frequent choppiness and dropped frames with those retroarch cfg settings.

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To my knowledge the Disk System is basically just a floppy disk attachment and underneath its running on the standard Famicom in terms of hardware so I DO NOT understand why its significantly worse in Retroarch than NES games. And good luck trying to play the Lost Levels with the default amount of input latency, the game is already hard enough! Anyone have a similar experience?