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I'll be upgrading my aging E6600 conroe system soon, and the new Athlon Propus 620 quad core has caught my eye, as has the unlockable Phenom II x2 550. A quad core for $100 isnt bad, no matter how you slice it. What I'm stuck on though, it whether to get an AM2+ board that supports DDR2 memory, or an AM3 board that supports DDR3. Note that these are both AM3 chips. I'm a little open on the price, but I do have to pay for a wedding, so I can't go crazy. That's why I'm considering the AM2+/DDR2 board: it will let me reuse memory that I currently own, instead of having to purchase more.

I use the system typically for development, and some light gaming. I'll normally have 2 or 3 VM's running, along with 1 or 2 instances of visual studio, plus all the ancillary programs that go along with programming.

What I want to know is: will selecting the AM3/DDR3 board provide a noticeable speedup in application execution (launch time doesn't matter to me) over the AM2+/DDR2 setup, given that everything else in the system is being held constant except socket and memory type?

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up vote 5 down vote accepted

Caveat: I've not used a DDR3 rig yet, so this is based on conjecture as much as anything else.

DDR3 is faster for bursts of activity but has higher latency than DDR2, so while it should be faster for most tasks it might not be for all and the latency may reduce the resulting performance boost. So unless the price difference in the boards is really small, I'd stick with the DDR2 and reuse the existing RAM. In fact I'd probably stick with DDR2 anyway. You can always upgrade the motherboard and RAM at a later date.

For your "light gaming" it will make no noticeable difference. My DDR2 based machine plays Crysis at 1920x1080 with everything in high quality with only one place in the game where it even stuttered (and I think the graphics card was the bottleneck there, not the rest of the system). Having DDR3 RAM on your graphics card will make more of a difference in gaming than the better RAM on your main board will - the tasks GPUs tend to perform benefit more from it than current generic CPUs will and with modern games the graphics card is more likely to be the key bottleneck rather than your CPU or RAM.

For VMS I'd wager that the overhead of context switches between VMs and other virtualisation overheads will pretty much dwarf any difference you get by the DDR3 memory being able to send them blocks of data faster.

For development: unless you are doing serious number crunching on large datasets (if all your inner loops work on small datasets, they'll be sat in cache the whole time anyway), you are not going to see much difference. While visual studio is fairly heavy it is not going to overly tax a machine enough to see the difference, database work too - your CPU will spend more time waiting for disc IO then it will waiting for memory reads.

Also remember that modern CPUs come with large L2 caches built on. Most tight, and many not so tight, loops will be served by that cache rather than needing much by way reads from main memory - and if you have many processes active at once to the point where all your L2 cache is getting clobbered each time around the scheduling queue then the overhead of context switches is going to dwarf any difference in bulk RAM response (and that higher latency is going to kick in too).

When I bumped my CPU up a couple of notches some months ago I kept my existing AM2+ board for the above reasoning, and haven't had any regrets saving the cash. Well, when I say "saving the cash" I mean "spending the cash on other stuff like a better graphics card and an extra hard-drive". DDR3 is currently, IMO, for people who don't have to think about spending the extra, especially people who are doing a fresh build and don't have to consider the economy or reusing old RAM, hardcore gamer types who must have the latest+greatest+fastest everything and believe every bit of marketing hype (they are like audiophiles at times), or people doing specialist computational work that needs the extra bulk transfer speeds between RAM and CPU.

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I hear you saying that the advantage of using DDR2 is that you can reuse your RAM.

Well, how much do you have? If it is only 1 or 2 GB of RAM, and you want to have dual channel and 4GB total RAM (or more), then you'll probably totally replace your memory anyway. If that is happening, DDR2 and DDR3 are roughly the same price and you'll want to do DDR3 for the performance improvement, some power savings (and less heat inside your system), as well as ease of finding replacement or upgrade RAM in the future.

The only reason to stay with DDR2 is if you can't afford $100 for more memory and you feel you can get by with the quantity of DDR2 you currently have.

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i think that getting a fast drive will improve your work more that going to ddr3... at the end your computer is fast like the slowest of the component, and the hard disk is the slowest of all...

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You're right, but you didn't answer the OP's question... – Sasha Chedygov Oct 29 '09 at 22:21
A fast drive will mostly help on initial load, and the op states launch time doesn't matter to him. – Phoshi Oct 29 '09 at 22:58
Depending on what the development work he mentions involves, a decent disc I/O subsystem could make a noticeable difference to ongoing performance as well as initial load times. If he is doing database work either with large datasets (that won't fit in RAM whole) or circumstances that involve many write operations or both (many writes to large datasets), for instance. If the machine ends up swapping with VS+DB+VMs+other then it'll make a bit difference (though adding more RAM would likely be more cost effective than getting high-end drives). – David Spillett Oct 30 '09 at 13:05

Yes. DDR3 is significantly faster, and the quicker your CPU can get the data it needs the quicker it can act on it.

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