I desperately need a new computer. I've decided that I'm going to get a good motherboard and a fast 45nm core i7 processor to build a pc.

My question is: in a few months, the price of 32nm processors will go down. Therefore, I would like to get a 45nm processor now and exchange it for a 32nm processor in about 6 months or so, keeping the same motherboard and memory. Is this possible with current motherboards? Is this a good idea? I like the fact that 32nm processors run cooler and therefore quieter.

As of right now, the only Intel desktop chips that are 32nm are Gulftown (6-core, LGA1366) and Clarkdale (2-core, LGA1156). Unfortunately, the 45-nm to 32-nm transition is gonna be on three seperate platforms so let's try to go through the options:

The LGA1366 platform, on which Bloomfield (original 'Nehalem' chips, such as i7-920) and Gulftown are based, should be around until at least the end of 2011. As of right now, you have two options on this platform: quad-core, 45nm chips, or hex-core, 32nm chips. It might be possible that they release a quad-core, 32nm chip, but I haven't heard any rumors or seen any roadmaps that indicate that this is gonna be the case. So in this route it might be possible to upgrade to a quad-core 32nm processor, if they ever release one.

The LGA1156 platform is what's used today for the 32nm Clarkdale chips (2-core) and the 45nm Lynnfield (quad-core) chips. Again, each chip only satisfies one of your requirements (either only 32-nm or only 2-core). Again, it might be possible that in the future, they release a 32-nm quad-core, but I haven't seen any roadmaps or heard any rumors that support this.

The only guaranteed Intel 32-nm quad core processor platform is...not released yet. That will be the LGA1155 platform, which will be the first platform for the new Sandy Bridge series. This will be 32nm, quad-core, hyperthreaded, and have an integrated graphics controller (one that supposedly has cache coherency with the CPU core...cool?). This platform will predictably not be compatible with current chips, so no chance that you'll be able to throw these processors into a motherboard you buy now.

So if you need 32nm right now, you're gonna have to either spend $900 on a 6-core LGA1366 processor, or only get 2 cores on an LGA1156 procesor. If you can wait out until the end of the year, you'll get your quad-core 32nm processor on the LGA1155 platform. I don't know if overclocking is important to you, but I've heard rumors that they're gonna seriously limit overclocking on this platform, as it is supposed to be a 'mainstream' platform. You'd have to wait until the replacement of the LGA1366 platform to get serious overclocking with lots of 32nm chips (unless you pony up for Gulftown right now)

One last thing: the only platform right now that can support both 45nm and 32nm processors and have 4 or more cores is the LGA1366 platform. Unfortunately, you either get 4-45nm cores or 6-32nm cores, so actually power consumption is the same. Of course the 32nm cores get multithreaded jobs done faster, but if you're just looking at it at a rough 'which generates less heat' standpoint, they are both at a wash right now...unless they come out with a different processor soon...

Seriously, knowing Intel, any new series of chip will require a chipset/ motherboard upgrade....
Ya can't beat AMD for their upgradability

Amen!

Choose something cheap that you don't mind throwing away once P67 chipset i7 2600 becomes available, eg. H55M_S2 is available on NW now. Keep the overexpensive memory you can currently buy with the new socket 1155, it will drop in price the next 5-6 month period or so, likely to be twice capacity same price.

If you want cool and quiet then you should go with the LGA 1156 socket and get a high clock speed two core i5 32nm processor now, and then upgrade it later to a four or even six core down the road. From what I’m reading, the LGA 1156 will be supported for another 1.5 years so there should be plenty of new chips to follow for what is Intel’s most popular socket. The i5 650 to i5 680 chips say the have a TDP of 73 watts, but that’s including the integrated graphics. If your not using the IGP then it will be pulling even less and therefore running cooler and more efficient. Probably somewhere in the 60w TDP range. An i7 is going to be 82w, 95w, or even 133w TDP depending on your choice.

875K is likely the last of the 1156, no 32nm down the road, just big hot chips based on 3 year old 45nm process. As for 1155 it will support maybe even 22nm in 2011-2012, just before DDR4 changes the socket in 2012. By the time of 22nm, the old 45 will be full stop, so is the 1156.