memory frequency vs. FSB frequency

K

kjk

Geek Trainee
I am considering to do an upgrade, later this year, and before that I am doing some homework.
The processor I had in mind is the Intel Core2Duo E8400 3GHz, 1333MHz FSB (bang for the buck, as they say). I thought it would make sense to have the memory frequency running at the same pace as the FSB. This leaves me with one option: DDR3/1333 MHz.
I can either choose between a motherboard that supports DDR2 or DDR3 (a little more expensive too), in the former case DDR2/1200MHz is probably the second best choice, the DDR3 choice would make more sense, the question of course is whether this is noticeable. However, at present there seems to be little performance gain of DDR3 over DDR2. Is this true? Also a reason to wait somewhat longer:).
Could you help me a little with my homework?
Thanks
 
Welcome to HWF :)

DDR2 means that the memory can perform two actions at each clock cycle. DDR3 can even perform three actions. Now if the CPU runs at an FSB of 1333 Mhz, you need to divide it by two. So that makes 665,5. The RAM speed that comes close to that, is DDR2-667. So if your memory is DDR2-667 or DDR2-800, your memory has the same FSB speed as the CPU.

So to summarize, the FSB speed is twice the amount of the DDR2 speed, and even three times the amount of the DDR3 speed. So DDR2-800 is (800x2) 1600Mhz. And DDR3-800 is (800x3) 2400Mhz.

And about your question of the speed difference between DDR2 and DDR3, this is indeed noticable. When choosing a motherboard, make sure that it supports the RAM that you're attempting to use. DDR3 ram won't work in a DDR2 slot. If you are ever attempting to buy an Intel i7 CPU in the future, then a DDR3 board with DDR3 RAM is even required.

*NOTE: My statement here is incorrect. I've corrected this below here, in this reply*
 
Thanks for your answer. So ddr3@(anything above 1333/3 MHz) has no advantage as you're implying.
There was on guru3d I believe a test with this cpu and they used ddr3@1333 ram. A bit confusing then.
I don't think there is ddr3@444 Mhz anyway, so ddr2@666 is the best 'fitting' memory for this cpu/FSB combination in theory as I understand.

There is also the latency aspect of memory, but that is a matter of chosing the lower=better in principle.
 
addendum:
I was thinking:): suppose ddr3 ram runs at the same speed of the FSB frequency, and suppose one read request from the FSB has a latency of 3 cticks, then that would mean that after one read request from the FSB, with the next ctick of the FSB, data would be ready from ram (1333/3cticks *3data blocks, so hypothetically in this case ddr3@1333MHz would supply 1 block of data one ctick after one read request from the FSB. Not sure if it works that way.

"If you are ever attempting to buy an Intel i7 CPU in the future, then a DDR3 board with DDR3 RAM is even required."
Sure, but don't expect to take any ddr3 ram from core2duo to i7 with you. By that time, I can trash the whole lot and start afresh:O.
 
If the RAM is DDR2-667, you can use it with that CPU if the FSB of the CPU is actually 1333 or less. But if the CPU has a higher FSB (can be controlled by the BIOS, and can even happen automatically in some cases), the 667 might not be sufficient. My personal advice when using the C2D is installing DDR2-800 or faster RAM.
 
I was also considering ddr2-800 as a minimum. ddr3 seems to have a higher latency than ddr2 and is useful at higher clockspeeds (1333 at miminum). When ddr3 came out it had a higher latency than currently is the case so ddr2 was still the better choice. Latencies may drop still somewhat and that will have more effect than higher clockspeeds.
It is all a matter of value for money, and will ddr3 (motherboard and memory) be noticeable for your personal applications (games in particular). A wild guess 5%, probably not above 10% improvement in fps, so not dramatic anyway. I think a videocard benefits more from ddr3 than ddr2 considering the fact that is deals with large matrices of data and the data the cpu gets is less structured that way, I suppose.
 
Wait a minute...I just mixed up something here. DDR stands for Double Data Rate. DDR always performs two operations at each cycle. The E8400 has an FSB of 333 MHz. To get the FSB you need to divide the DDR number instead of multiplying it. So 333 * 2 = 667. So the lowest amount to use is 667. This starts at DDR2, so you must have DDR2-667 or higher, or any DDR3 type, because DDR3 starts at 800.

I'm sorry that I wrote it wrong in my previous replies. This is the correct statement.
 
My choice will (probably) be:
Crucial DDR2 800MHz 1GB (4-4-4-12)
compare timings with a Kingston DDR3, 1600MHz, 1GB CL9 (9-9-9-27) and twice as expensive.

AMD processors are more sensitive to latencies than Intel processors are, so I've read. I don't overclock (probably), but this is also a way to optimise the speed with relation to the latencies. I don't know if the 4-4-4-12 timings are optimal for the 3GHz of this processor. Sigh. Oh well, I am not in a hurry.


A general rule of thumb applies here too, better one of the last versions of a previous technology than one of the earlier versions of a newer technology. That's why the processor is a good choice too, it consumes only 65W max with similar power consumption for the videocard I had in mind.
And BTW if you skip Vista and wait for Windows7(SP2), you will have enough with a mere 2GB of ram.;)
 
kjk said:
My choice will (probably) be:
Crucial DDR2 800MHz 1GB (4-4-4-12)
compare timings with a Kingston DDR3, 1600MHz, 1GB CL9 (9-9-9-27) and twice as expensive.
Click to expand...
DDR3 has indeed much higher timings than DDR2. That's why I still prefer DDR2.[/quote]

kjk said:
And BTW if you skip Vista and wait for Windows7(SP2), you will have enough with a mere 2GB of ram.;)
Click to expand...
I've tried a Beta version of Windows 7, and the RAM usage was even higher than Vista. It uses about 1024-1500MB of RAM without any programs opened....[/quote]
 
Actually, DDR2 1066MHz (5-5-5-15) has a higher latency, but more bandwith and that's more important. I have do some maths.

RHochstenbach said:
I've tried a Beta version of Windows 7, and the RAM usage was even higher than Vista. It uses about 1024-1500MB of RAM without any programs opened....
Click to expand...
:eek: While some say it is more resource efficient than its predecessor...:confused:
I stick to XP(lite) anyway, and Linux probably forever.

Windows7 is like ddr3 not matured, perhaps after SP2 who knows.
One disadvantage of XP is that it only supports DX9, while all hardware is DX10 these days. There seems to be a DX10 for XP (Alky project) but the few games I like are DX9 anyway, and an OpenGL one for Linux. DX10, politics played part in it no doubt, was to promote Vista. (And DX11 is the next promise now.)
 
kjk said:
One disadvantage of XP is that it only supports DX9, while all hardware is DX10 these days. There seems to be a DX10 for XP (Alky project) but the few games I like are DX9 anyway, and an OpenGL one for Linux. DX10, politics played part in it no doubt, was to promote Vista. (And DX11 is the next promise now.)
Click to expand...
DX10 is real failure. It doesn't have any advantages over DX9, but makes your graphics card to overheat. I've also noticed on a very large amount of computers with a DX10 graphics card, that all these cards start to get unresponsive when playing games in DX10 mode.

When I'm playing a game in Vista, I always set it to DX9 mode, if possible.
 
This is incredible, what a load of junk.
If you look at the power consumption too of the higher graphics cards, especially the nvidia ones:doh:.

Do DX10(.1) cards have DX9 settings, in the sense that they make use of DX9 efficiently? DX10 is not downward compatible with DX9, like DX9 is with DX8 e.g.
DX10 is supposed to make more efficient use of hardware, that is what we are led to believe anyway, as well as the DX10 graphics are more realistic (given the examples of DX9 vs. DX10 graphics shown). I doubt if the games I like will be upgraded to DX10, better not then.

Alas we are stuck with DirectX when games are concerned and can't choose for an OpenGL graphics renderer too, except for a few games running on Linux (also).
 
DX10 hardware is compatible with DX9. But DirectX 10 itself (the software) is not backward compatible with version 9. That is the reason why you need to install DX9 on Vista when playing a DX9 or older game.
 
On fora I know of some people running DX9 games on Vista, new to me that they have to install DX9 to run those games and uninstall then DX10 (which is probably not so easy according to MS). That would mean two Vista versions then, at least to play DX10 games as well??:x:
 
kjk said:
On fora I know of some people running DX9 games on Vista, new to me that they have to install DX9 to run those games and uninstall then DX10 (which is probably not so easy according to MS). That would mean two Vista versions then, at least to play DX10 games as well??:x:
Click to expand...
That's not true, unfortunately. You don't need to uninstall DX10. It's not even possible to uninstall DX10. You can install DX9 and DX10 next to each other, without any problems.
 
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