FPS goes down after upgrading hardware

Game was running fairly nice on Geforce GT 520 2GB DDR3 (though there were some issues which I've described in https://mojang.atlassian.net/browse/MC-1439).
Changing graphic card to ATI Radeon HD 7750 1 GB DDR5 (which is a lot faster than previous one) and newest drivers made it almost impossible to play - runs 4-8 FPS always. Optifine do not change anything.
Other games now runs a lot smoother.