hi all can some please enlighten me as to the difference of these CPU's?thx!

Clayton,The 754 are the older/hotter running processor that is being phased out by AMD. The 939 is AMD's current "64bit" processor used by most system builders utilizing a newer instruction set (MMX, SSE, SSE2, 3DNOW! Professional). Suggest buying a motherboard using the NVIDIA nForce4 chipset and AMD's 90 nm Winchester or Venice Core processor (runs cooler).

Hi Clayton, the biggest difference between the 2 CPU-types is that the 939s can control 2 memory channels where the 754-er is 'only' single-channel. Which instruction sets are supported depends on the CPU-core (aka Clawhammer, Newcastle, Winchester, etc). The same is valid for their energy consumption. I'ld also recommend a nForce chipset if you're considering 'mondo 64'. Good luck and kind regards Jaap

hi thanks for your responsehowever i really wont be upgrading for another 2 years min after this upgrade so you still think its worthwhile to upgrade to a 939 instead of 754?cause i want to use my PC2700 DDR 512meg stick from this computer onto the new one and my current 6600GT V Card.

also ive noticed that most of these motherboards supporting the 939 AGP slots req a 1.5V Video CARD, so is my current Leadtek 6600GT 128Meg Card 1.5v??

Hi Clayton, I'ld go for a board/platform with a socket 939 nForce4 (w/ PCI-e and S-ATA-300) instead of a nForce3 (w/ AGP and S-ATA-150). I see you have a 21" monitor and IMHO, a new 256MB/256-bit display adapter will serve this monitor better than the 6600GT and specially if you use FS at greater than 1024x resolutions. The RAM is no prob, you'll only loose a few % of the max possible performance when running @ a FSB of 333MHz instead of 400. I guess you're aware that 1GB is better too. I wouldn't mix different types of RAM with AMD64s and you should try to use identical modules (to date; max 2 pcs if the modules are 512MB or bigger). SInce the RAM is controlled by the CPU, this can be a pretty finicky detail sometimes. Generally, I'ld recommend modules with standard CL3 timings and Samsung chips. The price difference between the 2 sockets is marginal since the CPU prices are identical and only the price of mainboards vary. I believe upgradeability will be better with the nForce4 if you plan to use the platform for more than 2 years. Another important detail is the power supply; you'll need one with enough juice on the 12V rail (ca. 18-20A or more). Hope this adds to thoughts, good luck and kind regards Jaap

I dwelt on this for a long time. Taking the view that even the 939 socket may be obselete in two years time, I chose the 754 chip because for the 3700 it had a larger cache the 939s (but this was six months ago so needs checking now). Cache makes a lot of difference to performance. My 2Ghz Centrino is as fast as my older 3Ghz chip partly due to 2Mb of cache.

Jaapso will i be able to use this AGP CARD in an AMD 64 mobo, it says AGP 1.5V only is this ok ?

@ Clayton, yepp, all modern AGP mainboards are intended for use with 1.5V AGP-adapters. @ Howard, whilst I agree that the CPU cache can help, IMHO, the big difference with Centrinos is their technology. Just like the AMD64 with its technological advantages over the Pentium. If cache alone was an argument, we should all be running for 2MB Pentiums at 3.X GHz. OTOH, the 3.2GHz P4 Prescott with 1MB cache was actually slower than the 3.2 Northwood with 512kB. FYI, I'm looking into my next upgrade too and I'll probably get the 3700/939 San Diego with 1MB cache. Mainly because I don't want to go backward from my 1MB 3200 Clawhammer 754 which has been in use for almost 14 months now. Btw, I maybe shouldn't call this operation an upgrade because it's more of a crossgrade than anything else..? Hope this adds to thoughts, good luck and kind regards Jaap