According to posts on AMD his forums some of the Bartons like the Athlon XP 2500+ dated week 39 and later have multipliers locked. Some people have tried unlocking them but it won't work.
On a Dutch overclocking forum, we have also spotted several locked Bartons, all of them were in the list above. Sad that AMD did this. Some people have tried to unlock them(pinmod), but that didn't work. It really is too bad, since overclocking beyond 2,5Ghz is kinda hard with a fixed multiplier of 11
locked
AQFZA 0341 XPMW
AQXCA 0340
AQXFA 0339
AQXFA 0334
AQYFA 0342
AQZEA 0341 (?)
AQZFA 0342 UPMW
AQZFA 0339 UPMW
And possible more
unlocked
AQZEA 0339 UPMW
AQZEA 0334
AQZFA 0340
And everything before week 39
The reason why AMD did this is most likely not because they hate overclockers, but because of fraud by vendors who sell Athlon XP 2500+ processors as 3200+ ones.
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