How to Stop Mozilla Firefox From Consuming CPU Cycles? Open Firefox Browser on your computer. Type about:config in the address bar. Read the statement and click ‘I’ll be careful, I promise!’ button. Type “browser.cache.disk.capacity” in the search bar. Double click on the line and then modify the value to 16384. Now press Control, alt and delete key on your keyboard. CPU Usage for Firefox should now stay nominally under 20%. This is How you can stop firefox from consuming cpu cycles.