Not sure the exact cause, but i was trying to play "there be biters" with subsurface as i thought it would be a cool challenge, but part way into playing it my UPS tanked and i had an annoying stutter. When i checked my stats it said the subsurface's world gen was like 1/1/800.

I will admit i had installed more AAI vehicle stuff because i was wanting to automate clearing out a large space underground and had started working on doing the edges for the first room, but i did not have a massive amount dug compared to other playthroughs.

Here is the save file for the save with the UPS issues. I still had it, i am not sure if its right before or in the middle of the ups issues.
https://mega.nz/file/ZRgGFYKJ#Y2M_og0jhvh4MRiEqv1p6_p8UEJ_rrOZdzfhl7Wv9OM

I don't have huge UPS issues in that save

https://i.imgur.com/cSf88XX.png

You sure you loaded it correctly? For me as a move around it spikes down to 45 with a noticeable stutter.

Figured out it is the pollution handling, I'll think of a way to decrease it

Perhaps just letting the pollution spread in the void like how factorismo1/2/3 does it. I understand the want to keep the pollution located to only the dug areas, but if it is causing big UPS issues it might need to be compromised on.

+1 to the @Vinoren

I made small base (can barely name it base), made 2 levels with bore. Placed few miners on the 2 level with few air vents on all 3 surfaces.
As result my game started to freeze every 1-2 seconds for a 1-2 frames and UPS was dropping to 57-55 all time, while there was barely anything placed.

So if its pollution makes UPS to drop - it must be optimized or compromised on as @Vinoren said. Idk how I can help but I belive in u @Natha :D

P.S. Ryzen 9 7950X + 3080 Ti - should be enought to run that easy on 60 UPS.

I just made it more efficient, please have a test: https://github.com/NathaU/factorio-subsurface/tree/pollution

How do i test this? I am unfamiliar with downloading factorio mods from github and installing them.

Download the zip, extract and rename the folder to Subsurface_1.1.8

Massive improvement, but still a decent usage from the underground. from 200 to 50. Since the next biggest thing is 1.35 in scripts or 3 overall. More so since my save is pretty early game.

https://i.imgur.com/MR59WCJ.png

I figured out this is another thing than the pollution, my guess is the enemy handling. I'll try to improve that too