Method and system for managing a speculative transaction in a processing unit is provided. The speculative transaction is initiated by dispatching a first instruction indicating start of the speculative transaction. One or more register file (RF) entries are marked as pre-transaction memory (PTM), in response to the initiating. At least one second instruction targeting at least one of the marked RF entries is dispatched, while the transaction is active, wherein the at least one second instruction writes new result data into the at least one RF entry. Previous result data evicted from the at least one RF entry by the new result data, is saved into a history buffer (HB) entry. The HB entry is marked as PTM, in response to the saving, wherein the processing unit, upon detecting a trigger, is rolled back to a state before the initiating the transaction by restoring the previous result data to the at least one RF entry.