if we can unlock all 4 cores in an amd x2 550be which is clocked at 3.1mhz and the temp is as it is as using only two cores <45c temp then would it be more worth than x3 and x4 amd proc with clock <3.1mhz before overclocking
what is the diff betwn them?
The temp apps just get their reading directly from the cores.
HundredIslandBoy is 100% correct. The second best option would be looking at the difference between your current "CPU" temp (as measured by Motherboard) and noting the difference between cpu temp and reported by core temp.
(Assuming you haven't already unlocked the cores, note the difference between CPU Temp and Core Temps using a program like RealTemp)
Then you can use that as a way to gauge where your cores are at (at least, get a feeling).
However, you should use common sense and exercise caution when overclocking without any core temp indicator.