I've overclocked my Phenom II 720 to 3.4ghz with the 4th core. I want more, if it's possible, but I don't know what to do next.
I've tried 3.5, but that's when the errors show up and changing the voltage doesn't help. I'm wondering if my memory settings could be an issue. I really don't know if, or how memory comes into play with overclocking.
Also, do you think 3 cores at a higher clock would be better, or should I stick with the 4 cores?
Your mileage may vary, is always the case with overclocking. Most of the early Phenom II chips like the 740 can reach about 3.6GHz on air with no overvoltage, but that's best case. Besides, as you mentioned you have unlocked the 4th core, which will very likely affect your OC stability. I think chances are quite good you will achieve a higher OC with only 3 cores enabled.
Your choice will likely depend on what you want to do. Benchmarks suggest that the majority of games today wil run faster on a higher clocked triple core than a lower clocked quad, all other things being equal. If productivity rather than gaming is your thing, a stable quad wins every time.
Nope. I like gaming. I guess I can always do both settings and then just load that profile in the bios depending on what I'm doing that day.
My biggest concern was about the memory though. From a couple of guides, I've heard that at some point you kind of have to overclock the memory or something since that can be holding you back. That's a little beyond me and I was hoping someone knew how that worked and could explain it to me.
How are you overclocking? Increasing the reference clock speed or just changing the CPU multiplier?
If you are doing pure CPU overclocking, you don't need to worry too much about the RAM. Changing the system clock ref however will affect all components including RAM, in which case you sometimes need to loosen the RAM timings to achieve stability.
RAM and CPU share the FSB frequency. Your current RAM speed is the bus speed multiplied by the RAM multiplier (or ~ratio). Since RAM and CPU share the FSB, when you increase the speed/frequency of your CPU, you're also increasing the speed/frequency of your RAM.
What this means is, yes, you do have to overclock your RAM, sometimes, when overclocking the CPU. One of the reasons why you have instability after overclocking is because the RAM cannot handle the increase. This will all sound like gibberish unless you provide your RAM specs, or at least a link to it from newegg.
If you post your specs, we can try to help you attain a higher OC.
Then you shouldn't have to worry about the RAM, but if you want to be absolutely sure, loosen the timings to something like 9-9-9-20 and see if that improves your OC stability. I still suspect your unlocked 4th core just cannot be pushed any further.