(A) CPUs
Intel has a conroe core 2 duo cpu which is currently the best cpu out there but not cheap, specially the motherboards are quite expensive. Best performance, lowest power consumption, best performance per dollar BUT a lot of dollars. If you buy intel you want a conroe and a motherboard that is fully conroe compatible, there are only a few of em. Some of the 975 chipset motherboards and all of the 965 type motherboards. Currently the 965 boards come out slower but most people beleave with bios updates they will be on par soon.
Conroe is 1 silicone chip with 2 coupled cores which have 1 big L2 cache together, making it fast to transfer data between the cpus and providing max performance by "uneven" split of the cache. One core may get 3mb from it while the other one gets 1mb, giving them much better memory performance than a 50/50 split.
Verry complicated memory controller and shorter pipelines hide the low latency of the ddr2 memory.
- Pretty fast
- Low power consumtion
- Overclocks like hell
- Best performance
- Quite expensive
- Must have DDR2 RAM
AMD Has the AMD64 x2 CPU, which is a bit older than the conroe part and can be obtained for socket 939 and for AM2. AM2 is the new socket and runs with DDR2 ram just like intel conroe, 939 is older and verry reliable as well as having cheap motherboards. Also there is an AMD64 which is single core, i. e. only one CPU on the chip. Single core compare to dual core in performance when they have the same clock speed at about 1:1.4 , so dual core is overall far away from double performance. Best chipset is the top of the line nvidia chipset (dont know which that is atm).
Good cpu which runs fast on 32 and 64 bit, it has the memory controller on the cpu (instead of in the chipset as for intel) which reduces memory access latency. 2 cpu cores with 2 caches on one chip, cache is 512mb per core. The cpus are linked with a "hypertransport" bus (pretty fast).
- good enough performance for AH
- ok power consumption, no heat trouble like Pentium D
- cheap overall system possible with ok motherboard prices
- can have DDR or DDR2 ram
- AM2 socket said to be able to run the quad core chip next year (never know for sure though)
- Slower than conroe
- smaller cache
- not good for show off (conroe is more en vouge)
In future intel and AMD plan on going for quad core cpus, while intel seems to be closer to it they just put two dual cores in one package, which will give some performance trouble. But AMD seems to be far away from quad core, they plan to have all 4 on one die which would be better though. I heard AM2 socket would support the quad core cpus, but that is not certain. The first Intel quad seems to be out soon and run on their current motherboards. But it will put down double energy consumption -> using to much power.
Old intel Pentium D chips are two single core chips in one package, use a lot of power and run verry hot, still if you dont care about that they are obtained cheap since they are slower and use more energy than the new conroes.
(B)Motherboards
You need one with the top of the line chipset, be it nvidia, intel or ati. Take care that it has the interfaces you need, some have no IDE (cant plug in old drives), no parallel port (throw away old printer) or whatever else had to go away to make room for the new and fancy stuff.
Make sure the ram runs in the motherboard, since some combos dont work. Most times it is best to buy ram+motherboard together so you can swap the ram if it doesnt work on that motherboard.
Current graphic card slot to go is PCIe , which is a serial interface and can be multiplied, that means you can have 1,2,4,8 or 16 lines for one slot. For graphics card it must be a x16 (16 lines slot). There are boards with have two slots for graphic cards they are either "SLI" or "Crossfire" compatible, which means they will run with 2 nvidia cards or 2 ati cards. Some of these switch the lines if you use 2 graphic cards, giving each card a x8 slot. The boards which deliver 2 times x16 are better.
SATA is the current interface for harddisks, but there are some diffrences in speed. Basically its one channle for each harddisk, plug in a small cable and it works... much better than ide installation wise.
(C)Graphic card
Currently Nvidia and ATI are the only ones that produce graphic chips that are worth it for gaming, the cards get made by other guys but inside is a nvidia or ati chip. The top of the line graphic chips need a lot of power (more than the cpu), therefor you need a verry good power supply. Be carefull with the names... the cheap chips are pretty close to the good ones, and more ram is not better if it is slower.
So while some cheaper cards offer 512mb ram they are not necessarily better than ones that offer 256 kick a** super fast ram.
edit: Saw your questions. Pentium D processors run verry hot and are slower than conroe, eaven if clocked higher. Fastest pentium D probably doesnt beat the cheapest conroe. I would stay away from them.
