I reformated my system recently and now when I run my game, it runs significantly slower than it used to. I have no idea why as I have literally not changed anything in my game before the reformat or since.
If you haven't changed your code / version of GMS then the issue must be elsewhere.
1) Have you updated all of your drivers to the same versions as before?
2) If you've installed newer versions have you tried rolling back to the versions you had previously? (ie. GPU drivers)
3) Is Windows Update fully updated?
4) Does your AV have the same exceptions and realtime monitoring settings as before?
5) Any software installed that you didn't have before that could affect performance?
etc etc etc.
Lots of things that could have changed after a reformat that could be causing the issue.
Edit:
You've tagged this thread as v2.3 which is the beta.
Does it run slower in the beta than in 2.2.x or vice versa, or has it been imported / upgraded from a 2.2.x project?