Klosteral :
If it is a 2.7GHz processor, which is part of the Dual-core range, then do I double the 2.8? Is it actually a 5.6GHz?
What does the 45nm mean as opposed to the 65nm?
Would I be better off getting a totally different processor (+\- $20)
No, having a dual core CPU does not double the clock speed, just the number of cores.
This means that your system can process more threads in parallel for a healthy bump in performance and responsiveness.
If the application can use more than one thread (multi threaded app), you will see much higher performance from it on a dual or quad core machine.
The 45nm and 65nm numbers refer to the size of the circuit traces used in the CPU core.
A smaller circut is generally better as it draws less power for the same speed and can usually be clocked higher.
Which CPU is best for you really depends on your budget and intended usage for this machine.
It would also be useful to know which components you already have.
Klosteral :
My current rig has a socket 939 AMD Athlon 3000+ with a 1.81GHz processor.
This is "rated" at 3.00GHz, allowing me to run applications at up to 3.00GHz.
Is it the same case with the E6300?
No, you are not quite correct here.
The Athlon 3000+ really is a 1.8Ghz CPU.
At the time it was released, AMD was trying to market the fact their architecture was far more efficient than Intel's at the time.
They did this by marketing their CPUs relative performance to the original Pentium arch (please correct me if it was a different arch).
What they are trying to say is that their 1.8Ghz CPU gives you the performance of a 3Ghz Pentium CPU.
Intel, on the other hand, does not rate their CPUs as such instead giving it a simple product number.
The E6300 is simply their designation for a 2.8Ghz, 2Mb L2 Cache, Wolfdale based CPU.
The number has nothing to do with the performance of it as it merely places it in a product category.
Technically speaking, all their 45nm dual core CPUs are exactly the same differentiated only by the stock clock speeds and amount of enabled L2 Cache.