terrible fps as of patch 4.20

my frames have been dropping to 10-20 constantly during games. dropping and raising back and forth making skill shots completely impossible, whats worse is it isn't the new map it's simple your client. my CPU and RAM are still nice and stable. and my internet connection is just fine. but i simply can't perform like this riot. if this isn't fixed soon i'll have no choice but to quit this game all together