its a case of trial and error, core 0,1,2 might work and 3 might fail, or core 0,1,3 might and 2 fail, or you might get all working, or you might be really unlucky and have 2 dead cores completly. i can get my 555 running on 3 cores only, the last core is dead, it will post into windows but thats it, any benchmarks or testing fails, and prime95 cant even start workers on it, so i run it as a tri-core @ 3.9GHz which is more than enough.
when i asked what the chances were of getting a good unlocker, the general comment were, there are not any, its completly pot luck, you might buy a dual core that unlocks to a 4.5GHz quad core, or you might get one that will not unlock at all.