Intel Core i7 - Choosing the Best Memory Kit

[saschikarl]

OC

Hey,
now i like to go for 3,8Ghz

Do you think i can use tis configuration(first to see if it is stable)
QPI:1,35V
LLC=ON
DRAM Voltage:1,65V
CPU Voltage:1,35V
RAM@1333
BLCK:19x200

What would you try?

System:
Asus P6T Deluxe
Corsair XMS3 DIMM Kit 6GB PC3-10667U CL9-9-9-24
I7 920
Samsung 1TB 32MB Cache
Noctua NH-U12P

Thank you!

Greets

 

[saschikarl]

@rob

help meeee

 

[Rob Williams]

You don't need to ask for allowance to test out new settings... half of the fun of overclocking is to just apply a setting and see what works. 3.8GHz might very-well work, but it'd be a tough one. Those settings you show there are fine... if it's stable at that, I sure wouldn't complain. Our chip wouldn't get that high, though.

 

[saschikarl]

You don't need to ask for allowance to test out new settings... half of the fun of overclocking is to just apply a setting and see what works. 3.8GHz might very-well work, but it'd be a tough one. Those settings you show there are fine... if it's stable at that, I sure wouldn't complain. Our chip wouldn't get that high, though.

But I'm afraid of killing the cpu ;-)(with so high settings)

Anyway,I'll try it ,-)

 

[Rob Williams]

Haha. It will take a LOT to hurt your processor, especially if you keep to reasonable settings. I wouldn't recommend going over 1.40v on the CPU... just to be safe. The temps on i7 can get pretty ridiculous, and adding voltage is just going to make it worse.

 

[Unregistered]

On Wikipedia for the i7 Core it says that any RAM over 1333MHz will only use dual channel. Here it is copied and pasted:

The Core i7 has three memory channels, and the channel bandwidth can be selected by setting the memory multiplier. However, in early benchmarks, when the clock rate is set higher than a threshold (1333 for the 965XE) the processor will only access two memory channels simultaneously. A 965XE has higher memory throughput with 3xDDR3-1333 than with 3xDDR3-1600, and 2xDDR3-1600 has almost identical throughput to 3xDDR3-1600.[14]

I believe this is a design flaw Intel is trying to hide. I contacted Intel's tech support and asked them but they wouldn't give me any information about this and told me to contact my motherboard supplier..

I need to buy RAM but now I am unsure of what to get.. 1600 slower than 1333? Help!

 

[Kougar]

Be careful when taking Wiki information at face value. If you look at their source for this information, it is not the most credible, and also not current. Early motherboard testing showed some BIOS's only were able to run in dual channel mode, it was due to very immature BIOS's. Hence why Intel told you to contact your motherboard manufacturer...

From all the memory performace data I have seen, claiming only dual channel works above 1333MHz speeds is completely wrong. Unless you are using a motherboard with an extremely early beta BIOS or some such, its bunk. Link

Wiki's are a great place to start your research, but never end your research with them.

 

[chooquette]

Hi,

I usually don't post on technical forums such as these because I feel am not enough of a geek to make a worthy contribution. Aside from pure explanation or definition wise articles about memory, this is the most sensible topic I've read for a very long time. So I had to register to post my compliments to the author and also ask for advice. So Rob, thanks for the great reading

Now to my conundrum. I have a i7 920 rig I just built to replace the one I made in 2002. It currently has 6Gb OCZ XMP 1333 Mhz triple channel kit with an Asus Rampage II Extreme. I have Windows 7 beta 7068 installed. I use a lot Photoshop and video programs and do plenty of multi-tasking. The other day, I noticed the memory usage reached 73%. It could be a memory leak due to the OS being at a beta phase. Nonetheless, at startup, the memory usage is at 42% and on average at 55%-60%. So I thought that it could be better to invest into density rather than speed with a triple channel kit. I am building a rig for a friend and he's willing to buy my memory kit so I could unload this quickly.

If this is the way to go, I'd like to get 12Gb in the form of 4x3Gb. Memory kits made of 6x2Gb have started to appear on the market but still are not very common, and 4x3Gb kits are even rarer with a premium out of my pocket's reach. I don't wish to take up all the RAM real-estate of my motherboard to keep some room of maneuver for the future as there are only 6 slots so I prefer to have 4x3Gb instead of 6x2Gb.

So, would it be a sensible idea if I buy just buy cheap 12Gb 3X4Gb unbuffered DDR3 1600Mhz 2X240DIMM 9-9-9 for less than $150? I can't find something affordable at a lower speed or timings. I emailed the vendor but seems like they don't want to give any advice on this matter despite the fact that I'm not asking for any guarantee but only an opinion as to the feasibility. As you may have noticed, this is not a triple channel kit so I won't be able to take advantage of the bandwidth innovation feature and also do some overclocking. It is not guaranteed to work with i7 processors either. Is there a real risk of incompatibility and would it be not worth it at all?

Sorry for the long posting , and any advice would be appreciated

 

[Merlin]

If this is the way to go, I'd like to get 12Gb in the form of 4x3Gb. Memory kits made of 6x2Gb have started to appear on the market but still are not very common, and 4x3Gb kits are even rarer with a premium out of my pocket's reach. I don't wish to take up all the RAM real-estate of my motherboard to keep some room of maneuver for the future as there are only 6 slots so I prefer to have 4x3Gb instead of 6x2Gb.

Always the more RAM the better, Photoshop will use a lot of RAM
I tried to see what the limit of RAM would be for your mobo, some are 12 gig max and others like MSI will go to 24 gig of RAM.
Double check your RAM limit

All in All a nice mobo

 

[chooquette]

Hi Merlin,

Thank you, that's a comforting reply

Yes, Photoshop just eats the RAM away.
I also wanted to use the extra RAM-room to use as a super cache. I think that besides from RAM density, this could improve my set-up even without having the niceties of a triple matched kit. What do you think?

This mobo can take up to 24Gb of RAM. But with only 6 slots, one has to be savvy as it can only be done with 2x3x4Gb with today's market offering.

 

[Kougar]

To be honest I don't think anything over 6GB is needed... most of the RAM usage in Windows 7 is from windows caching your most frequently used programs in memory. The more ram you have available the more programs and data Windows 7 (And also Vista) will cache.

Any triple channel kit will let you use two of them, and as long as the motherboard has six memory slots then they will function in triple channel mode. However unless you work with GB sized files in Photoshop, do 3D design work or video editing anything beyond 6GB is overkill. Most programs are still not 64bit and won't be able to use more than 2GB anyway. Photoshop runs fluidly smooth on just 4GB even when working with 6MP images or huge bitmap files.

If you want to eek out every last performance gain, a good quality SSD would give you tangible results and I'd suggest whatever money you save by only buying 6GB you could put towards one of those.

 

[ClemSnide]

Mixing different memory profiles?

Rob-- Thanks for a really great article, and an even better discussion! It really did answer my questions about which memory to get for my new system.

I'm savvy enough to install RAM, HDs, and PCI cards, but I'd be a little hesitant to actually populate my own motherboard with a processor. (One wrong move and that's $280 down the drain.) So, I'll likely go with a system builder, like iBuyPower or CyberPowerPC, and upgrade some components. The systems I've configured have top-of-the-line cooling systems, and I would like to push the i7 920 to a reasonable frequency-- which as the discussion indicates, would mean that it'd need 1440 MHz RAM. Being a belt-and-suspenders sort, I'm going with DDR3-1600 for that reason.

You also answered a question that has been lurking in my mind, that (for the timing profile) lower numbers are better. And that's where the question comes in. I've picked Kingston 3x2 GB DDR3-1600 8-8-8-24 modules, which come at essentially $115 (since you can't go with NO memory). If I were to buy more RAM later, would I have to go with the same latency profile? I could only find 9-9-9-24 and 8-8-8-24 ratings, but if lower latency memory is available, would mixing that in make a difference?

System components: i7 920 processor, 6 GB RAM. Asus P6T Deluxe V2 motherboard. WD Caviar Black 640 GB HD (32 MB cache). Coolermaster V10 CPU/RAM cooler. HAF 932 case. Sapphire Radeon HD 4890 Toxic GPU (when it comes out). Yes, I do play the occasional game

 

[Kougar]

You can mix RAM with different lancies, but the board will default to the slowest latency (and in some cases, an even slower latency) for compatibility reasons. It's not a big deal, and you can set the board yourself to the latencies specificed by the slowest modules.

For almost all desktop users I'm pretty sure 6GB is more than sufficient for the next several years. Even with four virtual machines and tons of other program running 6GB has been enough for me. It would require some highly specialized programs to need anything more.

 

[Unregistered]

My first i7

Hello,

thank you for the excellent article Rob!
Over the last few days I have been reading tons of articles regarding the i7 and memory.
Now this here article and the interview on XMP with Christopher Cox have answered many questions but some still remain.
I am building an i7 system for use with CAD programs. Thus it should be rock solid to guarantee a continues workflow. After seeing your benchmarks I understand that a kit of DDR3 ram at 1066MHz will be enough, if you plan to run at stock speeds right? I have the i7 920 and I think it came with the new D0 stepping, just not sure as I cannot run my pc at the moment. My problem is, in my area/country those kits are rare ... don't ask me why though. But above 1066MHz there's a huge range to chose from. Now I was wondering, if I take for example a kit @ 1333MHz CL7 7-7-20 it will automatically be downclocked to 1066MHz. But what about the timings will they remain at 7-7-7-20? Or will another profile be loaded from the SPD? And if yes in what range will those timings be? And will it be stable? logically I'd say that the timings will change, but I'm just not sure. Many of those kits makes use of voltages higher than 1.5V, will those be downscaled to?
Now most of these have XMP, and in the interview Chris states that XMP can overclock the CPU due to the FSB being changed. But with i7 it should be different at least with the D0 stepping and unlocked memory multiplier? Enabling the XMP would just up the multiplier and thus raise the uncore, given my 920 is D0. I'm not sure if those where all my questions but the post is long enough already and I hope it's not just plain rubbish I am asking.

With best regards Unregistered

 

[Kougar]

The memory will run at whatever settings you want to run it at. For example if it's rated for 1333MHz then you can run it at 1333MHz with a Core i7, most motherboards allow user selectable memory multipliers to adjust the memory frequency to the CPU speed.

I'd recommend going for whatever kits are the cheapest, beyond that 1333-1600Mhz is the sweet spot and CAS 7 is ideal if possible, but CAS 8 performs almost identically anyway.

XMP will only take effect if you enable it, you can always set the RAM timings and voltages yourself to specs. Especially the voltages. Most motherboards you buy yourself will allow you to adjust the memory voltage, just be sure to not buy a kit of memory that requires more than 1.65v.

 

[Unregistered]

Thank you Kougar for the fast response!

I find it comforting that you too have the GA-X58-UD5 !
As a matter of fact I do fancy a Corsair 6GB 1333 C7 kit, second choice would be a Kingston HyperX 6GB 1600 C8 kit (cheaper by 3 Euro).
Although I'd rather take Kingston over Corsair, the 1600MHz kit might just be out of my league. I don't know what's to it but in a recommended memory list for the GA-X58-UD5 it is stated that you can only put one 1600MHz DIMM per channel. And because I'm planing on going 12GB (the CAD programs will love it) the HyperX kit might not be my case. Will running them at 1333MHz solve this problem?
If yes do I have to find and set the timings manually then? Or will the board pick the best for me? The Kingston require 1.65V, will they still need such voltage at 1333? Is it just a crazy idea ?
Yes I know that I can run the memory at any settings I want and I know how to work the multipliers. My concern is the timings, will they be selected for me to match the speed I set and get a stable system? Must I find them by trial and error or should I just set them to match the on box specs regardless of the speed the memory is at?
Of course if my 920 isn't D0 all of the above won't be happening without overclocking the core. I'am not very fond of overclocking my new system as I fear it might get unstable. I know many people get really good results but I don't want to risk loosing my work because of sudden instability. In the future and with more time on my hands will I try it out.
Maybe I am just a bit to overcautious but I have been out of the loop since 2005.

Cheers Unregistered

 

[Rob Williams]

Hi Unregistered:

More often than not, if you purchase a high-clocked memory kit, you should have little issue down-clocking it. This used to be somewhat of a problem a few years ago, especially with DDR1, but I haven't personally experienced that issue with DDR3. I personally run a Corsair 6GB DDR3-1600 CL8 kit at DDR3-1333 CL7 in our benchmarking machines and haven't had an issue. Still, I can't rule out that it's never going to be a problem, but I think it'd be exceedingly rare.

If you purchase that Kingston kit, I have serious doubts you are going to run into issues. Personally, I'd go Corsair just to be absolutely sure, but if you are a Kingston fan, the chance you're going to take is minimal. Simply install the kit, boot up, set the RAM frequency to DDR3-1333, the timings to 7-7-7-20 (CAS/tRCD/tRP/tRAS) and the voltage to about 1.55v. If that's not stable, raise the ram in small increments, but don't exceed 1.65v.

It's not going to hurt, either, to simply pick up the kit you need and see if the board will run DDR3-1600 with 12GB of RAM, but it's certainly not going to be a game-changer. Personally, I'd rather run DDR3-1600 CL8 over DDR3-1333 CL7, mainly because we did see slight increases in performance. But again, if that doesn't run in a 12GB configuration, you're choice is pretty much made, and there's absolutely nothing wrong with CL7 at DDR3-1333.

As for overclocking, if you are taking your work seriously, just don't do it. If it was Core 2, I'd say sure, go for it, but Core i7 requires more attention to detail when overclocking, and especially more voltage, so I'd say you're better off just playing it safe, unless you want to spend a day or two tweaking and stressing the heck out of the machine.

 

[Unregistered]

Thanks!

Kougar, Rob - Thank you so much, you have made one Unregistered very happy !

Techgage has owned it's permanent bookmark!
Only place that really helped me with my questions!

Just to sum it all up, the Corsair was out of stock so I bought the Kingston. And after getting all the great help I am looking forward to finishing my new PC.

Great site! Great users! Keep it up!
Unregistered

 

[Rob Williams]

Techgage has owned it's permanent bookmark!

Woo hoo, we'll do our best to live up to the expectation that a permanent bookmark holds

Once you get your system built, let us know how it made out. As odd as it is, I've never personally built an i7 machine with 12GB of RAM, so I'm interested in seeing if you're going to be able to run DDR3-1600 or not (might as well try, won't hurt anything).

Good luck!

 

[Kougar]

Just a few last words, make sure to update your BIOS before installing 12GB of RAM, earlier BIOS's did have some problems with that much memory.

And if you are going to use 12GB, make sure you use the same RAM to avoid any problems... since you bought Kingston, make sure all of the 12GB is the same specification Kingston RAM. 12GB of 1600MHz RAM should work fine.