I have trouble understanding some stuffs.. im a complete hardware newbie. A couple of questions here...
1) What is dual core exactly? My brother has a Athlon 64 X2 4200+ 2.2 GHz .. which is dual core and mine is AthlonXP 3000+ 2.16GHz... how much better will his computer run? or is dual core only differentiable in the aspects of multi tasking?
2) How come most decent amd processors are at 2.0-2.5gh? What is the best/fastest one out there? All the intel ones i see are 3.0+
first, not all processor are creted equal. The Athlon XP was a good CPU in its time. The core was effective and could rival Intel until they released their Pentium 4 Northwood. To be efficient, the P4 needed higher clock speed, because it was not able to process ans many instruction for each clock than AMD.
To put it simple, 4 instructions X 5 clock cycle=20. That was Intel P4 way. On the other hand, AMD was doing more instruction for each clock cycle. So, it would be 5 instruction X 4 clock cycle=20. same result at the end.
The Athlon64 was then brought to compete with Intel good P4 northwood. It was an improved AthlonXP core (named K8) and they integrated the memory controller in the CPU, reducing latency. AMD was much more efficient by still doing more instruction for each clock cycle than Intel and the integrated memory controller helped in reducing latency caused by the FSB way of doing thing. Athlon64 don't have FSB. Intel still has. A FSB is the BUS that goes from the cpu to the memorycontroller in the northbridge then to the memory. On AMD cpu, since the memory controller is directly connected to the CPU, then the bust only goes from the CPU to the memory, leaving the northbridge for other thing than memory.
Dual core is simply 2 CPU core on the same package. so, your brother's computer is working almost like a dual CPU (2 CPU socket) system, but having only 1 socket, and 2 CPU using the same socket. Why his 2.2GHz CPU was able to outperform faster clocked CPU is all about cpu efficiency and integrated memoty controller. New Intel core2 processor run slower that current AMD and perform better. this is for the same reason, improved cpu core. But they still lack integrated memory controller. But good chipset care for that.
As you said, having 2 core only help when doing multitasking. If one apps use a core at 100%, you still have the other one to perform other task. your system will perform smoother than one with only one fully loaded core.
Which CPU is better? Don't buy a computer only by its CPU. $ for $, AMD and Intel CPU will give good performance. When I buy a new computer, whet I look first is the HDD interface speed. Even the fastest cpu will suffer from slow HDD. Newer Intel and AMD(ATI) chipset, in my experience, offer the best HDD experience. Nvidia old nforce4(or its descending design) offer average performance, by today's standard. Newer 680i improve on that side thou.
Then, I look at the motherboard's features, then I put a CPU on it, what ever brand will fit on. I often cut on the CPU side if I need more video performance for gaming.
Core2 have now performance advantage, but AMD still have good value. Better motherboard choice at lower price than Intel, and their CPU are now very affordable.
No matter the one you choose, you won't do wrong with either brand.