After unlocking, most cpu's will not reach their full overclocking potential. There is anecdotal evidence for this all over the web. Actually, 3.6 Ghz is very good for an unlocked CPU. I've seen a few of the black edition X2's reach 3.7 Ghz, and claims of 3.8 but I have not seen this with a cpu-z validation.
f you want to see if you can get 3.8 Ghz from this CPU, I would lock the 4th core again and try increasing the reference clock.
Some of the unlocked CPU's I've seen can only reach 3.2 Ghz, so you should probably consider yourself lucky to be stable at 3.6.
The core that was locked is faulty or doesn't meet specs. So an unlocked processor will never overclock as much as a locked processor.
For example the Athlon x3 445 I bought for someone last week clocked 3.9Ghz on stock voltage. I didn't want to unlock since stability issues can occur with a core that didn't cut the make the team. I don't want to be held accountable for blue screens lol.
Anyway the sheer clock speed using only 3 cores can definitely beat out an unlocked processor at low threaded applications.
Though a 4th core will almost always be better at highly threaded applications.
Yet most don't are not optimised for more than 2-3 threads anyway.