If your cache is not loaded fully it can reduce performance and cause lag, especially if you change areas suddenly, such as teleporting or going into an instanced area.
Cache can load whilst you're playing but it will cause a noticeable performance drop and will stop or slow down downloading if the client detects a significantly low FPS.
To check the progress of your cache:
- Open the client and use the key combination Alt and ` to open the Developer Console overlay
- Enter the command 'displayfps' in the overlay
- Close Developer Console by hitting Alt and `
- This opens a separate overlay showing your FPS and disk cache progress
On Windows your Disk Cache should be around 4 - 5GB when complete. On Mac your Disk Cache should be around 8 - 9GB when complete. If your cache is red or orange, allow your cache to load further before playing.
Check out more information on Improving RuneScape's performance.