I am deciding between the AMD x2 560 and amd x4 955. I read the reviews on newegg for the dual core, and they all said "unlocked to quad core, yay!" What are my chances on having the extra two cores? Also, how much can the 560 as x2 be pushed as far as overclocking goes? The 955 can go max 4ghz on air, but the x2 unlocked to quad has been oc'ed to 4ghz on air.
You never know why this CPU was binned as an x2. It could be that there is 1-2 defective cores, it could be that it wasn't 100% stable when clocked at 3.3GHz (or could meet it with default voltage). If you are lucky, it could also be that AMD produced too many X4, but needed more X2 so they just "disabled" 2 cores. Same thing would apply for OC, you cannot assume that all CPUs of a given model will OC the same, some might actually be very limited.
My suggestion is therefore to buy what you need, the extra will be bonus.
There is a saying: if you can't afford to loose, you can't afford to win.
I prefer the demotivator version:
However, it doesn't really apply to this situation .
The success rate is about 30-40% from the sounds of it, so not great, and far from a sure thing.
As far as overclocking potential, it depends on your board, cooler and why the chip got locked. If it had a core that needs more voltage you will end up with more heat and a lower overall OC, if it has a slightly leakier one that uses more power the OC should be about the same but there will be a lot more heat to deal with.
If you are doing stuff that will benefit from a quad, get a quad in the first place, dont hope to be one of the lucky ones who gets a 955 on the cheap, if you need it get it.
@Zenthar, i like the picture, i will have to save that one.
What are you going for, 4 cores only or the extra cache? If you just want the 4 core config with decent OC ability then I'd go for an Athlon II 640 and OC that. I suggest that because it sounds to me you dont want to pay 160 plus to get the sure thing.
If that's the case then you will be much better off getting a stable 640 instead of a flakey unlocked dual/ triple core.