Why my photoshop ps4 don't work with good performance?
I tested same variants of setting.
I've win 10.
When I work, gradually photoshop become very slow, but I've 16 giga of ram and a new processor.
Are you actually running Photoshop CS4? If so, that's a very old application and it was never designed to run on Windows 10. Heck, CS4 came out even before Windows 7. Have you considered upgrading to a newer version?
Beyond that, have you checked your scratch disk space compared to the size of the file you're working with? Also, are you running another process in the background? Do you have auto-save active?