Intel Core i7 - Choosing the Best Memory Kit

[Rob Williams]

Can't decide on the right memory kit to pick up with your brand-new Core i7 PC upon release? This article was designed for you. We aren't comparing brands here, but are rather comparing densities and frequencies against each other to see if there's any point at all in purchasing a higher-end kit. You might just be surprised at our results.

You can read our full article here and discuss it here.

 

[Unregistered]

good job

Thank you very much for the good work. The questions on everyone's mind will be what motherboard and how much and what type of memory to get. The rest of the computer can stay the same but getting one of the new i7 CPU's costs much more than just the CPU.

Your article has saved me some money.

 

[snakyjake]

Good article.

Not sure what kind of user I should be labeled as, but I'm a user that has many open applications, threads, and processes. I'm constantly switching between the applications. So I want memory that can make my experience better. Obviously adding more memory is going to speed things up. But with more memory, more memory bandwidth and transactions are going to be used. So the more memory, I figure the faster memory I need.

Maybe I'm wrong and any of the triple lane memory will be sufficient. Better then to buy the memory with the best value.

Thanks,

Jake

 

[BerZerK]

RAM for i920 OC to 3.2GHz?

Hi,
thanks for an interesting article.

I have already bought the Asus P6T Deluxe. I'm waiting for the i7-920 that should arrive by the end of this month here in Norway. I'm planning to overclock this CPU to 3.2 - 3.4GHz.
I have ordered any RAM yet. I think I need help for that part since it seems to me to be quite complicated to figure out any good info regarding this matter.

What kind of DDR RAM would you recommend for this?
DDR1066, DDR1333, DDR1375, DDR1600 or something else?
Anything about latency end memory timings?

Any concerns regarding the difference of the old DDR3 and the new DDR3?
Or is there no real difference?

If I run the i7-920 on 2.67GHz, DDR 1066 would be enought?

Thanks in advance.

Best regards,
BerZerK

 

[phconnell]

Do I have to overclock DDR3-1600

I have a Core i7 920 plus a Gigabyte GA-EX58-UD5 on the way and wanted to buy DDR3-1600 memory, for the future if I can get a faster CPU, with an unlocked core multiplier, in a year or two.

Problem is will the DDR3-1600 memory work if the BCLCK is 133 Mhz and I only have a x6 or x8 memory multiplier - no overclocking?

Does DDR3-1600 mean it works UP TO 1600 MHz and will work at lower speeds or does DDR3-1600 only work at 1600 MHz requiring the system to be overclocked for it.

It seems sensible that DDR3-1600 would work as a substitute for DDR3-800 or DDR3-1066 memory but I cannot find it stated anywhere.

 

[Rob Williams]

Hi guys:

Thanks for the comments! I'll tackle the questions one by one...

Obviously adding more memory is going to speed things up. But with more memory, more memory bandwidth and transactions are going to be used. So the more memory, I figure the faster memory I need.

As seen in the article, higher densities don't make a substantical difference with latencies, so getting a DDR3-1066 6-6-6 or DDR3-1333 7-7-7 isn't going to hold you back. Having one of those, I don't think you are going to see much better performance, really. I'd like to do more in-depth multi-tasking-related tests like this in the future, but it's a bit difficult to put together. I'm confident you'll be pleased with pretty-well any 6GB kit, though.

I'm planning to overclock this CPU to 3.2 - 3.4GHz. I have ordered any RAM yet. I think I need help for that part since it seems to me to be quite complicated to figure out any good info regarding this matter.

That kind of overclock is a bit extreme given the i7's real lack of high headroom, so I am not entirely sure you will be able to hit 3.2GHz or higher... just don't count on it. The locked multiplier of 20x means that the only way to overclock will be by increasing the Base Clock. To hit 3.2GHz, it'd have to be 160MHz, which seems to be on the edge of bleeding. You can always see what you can muster, but I don't think huge overclocking is going to happen with that CPU. I'd love to hear your reports though.

As for the RAM required to do so, I can't speak for certain right now because I'm unsure if the i7 920 limits the RAM multiplier. If not, then a DDR3-1333 kit is all you need... or even DDR3-1066.

If the i7 920 works like the i7 Extreme 965, then by boosting the Base Clock to 166MHz (which is a big overclock, the minimum RAM speed can be DDR3-996. Essentially, the lowest memory multiplier is 6x, but I'm just not positive it's the same way on the 920. I'll update this thread once I know for sure... I'll be doing a lot of rebenchmarking next week once we receive a new ASUS board in for testing.

I have a Core i7 920 plus a Gigabyte GA-EX58-UD5 on the way and wanted to buy DDR3-1600 memory, for the future if I can get a faster CPU, with an unlocked core multiplier, in a year or two.

You did read this article, right? ;-)

Like previous Intel architectures, the overall RAM speed is based on the Base Clock, and given the available multipliers available, DDR3-1600 should be easy on the i7 920. The same response as above has to be repeated though... don't quote me. I need to make sure that the 920 allows unlocked memory multipliers before I can state anything as fact. I'm assuming it will be no problem, but don't want to promise anything. I'll try to get this information before week's end.

Does DDR3-1600 mean it works UP TO 1600 MHz and will work at lower speeds or does DDR3-1600 only work at 1600 MHz requiring the system to be overclocked for it.

On Core i7, there isn't real overclocking involved with memory speeds. Increasing the memory speeds does increase the Uncore Clock, but that's fine up to 3200MHz, which means a minimum DDR3 speed of 1600MHz. So as long as the memory multipliers are unlocked on the mainstream processor models, anywhere between DDR3-800 and DDR3-2133 should be available without any sort of real overclocking (except the Uncore Clock, but that happens automatically, and may require a bit of a CPU voltage boost).

 

[DeathBooger]

Hey, I'm a 3D artist. While the time savings don't seem much for some of your renders, it actually adds up. If you're saving 3 or 4 seconds when using 6GB of DDR3-1600 vs. 3GB of DDR3-1066, it's worth it.

I usually create animations at 30 frames per second. Each frame counts as a single render. If I create a 30 second animaiton, that equates to 900 frames I have to render. Those 3 or 4 seconds saved per frame add up to an hour being shaved off of my render times. And that's just for a short 30 second animation. Imagine how much time a 30 minute animation would save.

You should give one of the example animations in 3DS Max a go and see how much of a difference it can be. I'm not clear on your experience level with 3DS Max, but all you have to do is make sure the Render Dialog is set to render all frames, check the Save File box, and that it's set to save the output file in some format such as AVI.

 

[DeathBooger]

Thanks for running these benchmarks by the way. I haven't upgraded in 3 years and have been out of the loop. I plan on getting a Core i7 setup when everything is released. I'm on a S939 4400+ X2 with 2GB of RAM. I remember when this was an awesome setup, but now my multithreaded benchmarks are the same in POV-Ray as a Core i7 920 in the single threaded test. Both of your articles on the Core i7 helped me a lot.

 

[phconnell]

Will my DDR3-1600 work with locked Core i7 920

Hi Rob,
Thanks for your reply. I am still not sure however. I did read the article but you used a Core i7 965 where the CPU and memory multipliers are unlocked and adjustable for most DDR3 memory, so I don't know what will happen with a 920 - which is what most of us will be buying.

My problem is that I ordered OCZ "Gold" DDR3-1600 (at 1.65 Volts) and then wondered if it would work on my Core i7 920 if I could not (or would not) change the memory multipliers. I presume that if the system is set for DDR3-1066 memory then substituting DDR3-1600 and rebooting will not cause the system to crash. I understand the multiplier system but what happens if my memory kit speed doesn't match them?

If the BIOS is set for optimum results with DDR3-1066, what happens if it finds DDR3-1600 memory on booting. Does it make automatic corrections to somehow find a new optimum performance or just continue blindly.

The question is what DDR3-FFFF means. Does is mean that FFFF is the limiting UPPER frequency (what I assume), or does it work ONLY AT that frequency and will have trouble if the system BIOS "expects" a lower frequency.

I am used to just plugging in my memory on my AMD systems and it always "works" but I am not sure anymore how the new Core i7 will react.

 

[Rob Williams]

It seems my assumptions were completely incorrect... there are memory limits when using a non-Extreme processor. I popped in the Core i7 920 earlier and the default (and maximum) memory speed was DDR3-1066, with the only other option being DDR3-800. Essentially, that means the memory multipliers are locked to 6x and 8x, and the only way to increase the memory speed is to increase the Base Clock.

So, bumping the Base Clock to 166MHz will boost the memory to DDR3-1333. I really couldn't imagine seeing the BCLK going much higher than that for most people, though. I did a quick test earlier with a BCLK of 167MHz and the memory speed at DDR3-1333 and it seemed incredibly stable. I haven't tested out the CPU's top-end overclock of 3.32GHz though (assuming most people wouldn't go above 166MHz BCLK, as I mentioned), but I will try to tackle it soon.

I usually create animations at 30 frames per second. Each frame counts as a single render. If I create a 30 second animaiton, that equates to 900 frames I have to render. Those 3 or 4 seconds saved per frame add up to an hour being shaved off of my render times. And that's just for a short 30 second animation. Imagine how much time a 30 minute animation would save.

That's true and I understand that, but as I mentioned in the article, my conclusions were based around the regular consumer... and you are definitely not a regular consumer with workloads like that. I did mention before (if not in this article, previous ones) that faster memory can benefit the professionals if workloads can take days to accomplish, because a few hours saved is going to be appreciated I'm sure.

In our results though, I really didn't see definitive evidence that faster memory guarantees a faster rendering time, regardless of how large the workload is. As you can imagine, we don't have access to these huge workloads, so we can only use what we have here. The most in-depth workload I could find on Autodesk's sample DVDs was the Dragon scene, which might be a good test for memory, as it would take around 30 minutes to render a full 60-frame 1080p scene, although it would require a lot more time on my part. I'll definitely consider a follow-up to this article, taking more intensive workloads into consideration. Thanks for the input, I appreciate it.

Thanks for your reply. I am still not sure however. I did read the article but you used a Core i7 965 where the CPU and memory multipliers are unlocked and adjustable for most DDR3 memory, so I don't know what will happen with a 920 - which is what most of us will be buying.

I mentioned the answer already, and yes, you'll be unable to take full-advantage of what the memory kit offers with your i7 920. As seen in the article though, you are very, very unlikely to notice any speed increase with the full DDR3-1600 speed though, so in a way, you won't be ripped off of any real performance. You did kind of throw your money away with getting a bigger kit though, sadly.

Does it make automatic corrections to somehow find a new optimum performance or just continue blindly.

It will just adjust itself to DDR3-1066, since with the given restrictions, it will be impossible for it to go any higher. The default memory clock in the CPU is 133MHz and the default memory multiplier is 8x, so it will result in DDR3-1066 at boot.

The question is what DDR3-FFFF means. Does is mean that FFFF is the limiting UPPER frequency (what I assume), or does it work ONLY AT that frequency and will have trouble if the system BIOS "expects" a lower frequency.

That figure is the max-supported frequency of that kit of RAM. Slower speeds will be programmed into the SPD, and that's what it usually defaults to at boot, unless the CPU comes into play and has something to say. The best thing is to just go into the BIOS and manually set your settings to make sure it boots with the correct frequency and timings.

As for plugging in the memory and it "just working"... that doesn't really happen with high-performance RAM. If you are running anything higher than DDR2-1066 or DDR3-1066, and never set anything in the BIOS, chances are it's running slower than stock. You can check the memory tab in CPU-Z to see if it's running at the correct frequency. You would just take the raw frequency, multiple by two to get the proper DDRx-FFFF rating.

 

[DeathBooger]

It seems my assumptions were completely incorrect... there are memory limits when using a non-Extreme processor. I popped in the Core i7 920 earlier and the default (and maximum) memory speed was DDR3-1066, with the only other option being DDR3-800. Essentially, that means the memory multipliers are locked to 6x and 8x, and the only way to increase the memory speed is to increase the Base Clock.

So, bumping the Base Clock to 166MHz will boost the memory to DDR3-1333. I really couldn't imagine seeing the BCLK going much higher than that for most people, though. I did a quick test earlier with a BCLK of 167MHz and the memory speed at DDR3-1333 and it seemed incredibly stable. I haven't tested out the CPU's top-end overclock of 3.32GHz though (assuming most people wouldn't go above 166MHz BCLK, as I mentioned), but I will try to tackle it soon.

I'm very interested in this information. I'd like to know if a 920 with the BCLK set to 166MHz is stable with the stock Intel cooler and if you have to modify the voltage setting at all. My plan was to get 6GB of DDR3-1333 and overclock a 920, but if it's too much of a hassle I'll just stick to stock clocks and DDR3-1066.

I've read that people are getting better successes with the ASUS board than the Intel board. I've seen people getting stable 4GHz and above with the 960. I'm more interested in the 920 though and no one else seems to be really covering it.

 

[Rob Williams]

I left the machine to stress overnight, and I can report that with a Base Clock of 166MHz and a 20x multiplier, the PC turned out to be completely stable, as you can see in the screenshot below. I didn't use the stock heatsink, but I wouldn't imagine any issues arising from using it. The temperatures would undoubtedly be higher, but I doubt it's going to throttle the speed or overheat. Still, it would be wise to keep an eye on the temperatures to make sure of it.

For that run, no voltages were adjusted at all. The CPU voltage kept at around 1.25v, while the RAM voltage was set to 1.60v. I also ran nine runs of 3DMark Vantage on the Extreme setting and it passed through each one without issue, so I'm very confident in saying that this is one very stable overclock.

Original Screenshot

 

[DeathBooger]

What did the temperatures look like vs. stock? Since it's basically the same clock as the 960 and they both have the same stock cooler for the most part, I would think it wouldn't be an issue. Thanks for doing all this!

 

[phconnell]

To Rob Wiliams:

Thanks for you help - the DDR-1600 might be useful in a year when CPU prices come down and INTEL scale Core i7 down to 32 nm, and perhaps give everyone unlocked multipliers for next Christmas.

The 166 MHz overclock is interesting as many people are swooning over 200 MHz BLCK speed and 4.0++ GHz speeds, but I don't know what their CPU looked like after a week or two.

It would be great if you, or someone else, could make a table of possible stable overclocking parameters for popular CPUs like the 920, with comments about the dangers of over-voltages or over- heating and revised lifetimes. I do a lot of number crunching but don't have time to tweak BIOS parameters for a week or two, but if a program takes two days to run instead of three then that is a real advantage for people like me.

 

[Rob Williams]

What did the temperatures look like vs. stock? Since it's basically the same clock as the 960 and they both have the same stock cooler for the most part, I would think it wouldn't be an issue. Thanks for doing all this!

I didn't check the temperatures clock-for-clock, but you're right... it's not going to be a huge issue. I do believe the i7 965 includes a more robust CPU cooler though, but I still don't think it will matter too much. After all, it's not as though you'll be pushing the CPU 100% constantly... I just can't see temperatures becoming a problem whatsoever.

I can assuredly say also that anything above 166MHz Base Clock is going to be sketchy. I tried to get the CPU to boot at 3.8GHz, and it just wasn't happening with reasonable voltages. Right now, I'm running 180x20 (3.6GHz) and it's rock-stable once again, both through 3DMark and the CPU stress test. Temperatures are 10°C higher than what they were with the 3.33GHz overclock.

I should also mention that the room temperature here is higher to begin with, so if you are in a room that hovers around 70°F, then you are automatically going to see much lower temperatures than me.

Thanks for you help - the DDR-1600 might be useful in a year when CPU prices come down and INTEL scale Core i7 down to 32 nm, and perhaps give everyone unlocked multipliers for next Christmas.

Well, as seen in the article, I don't think DDR3-1600 speeds are important at all, unless you happen use Adobe Lightroom or other image manipulation applications often. Even then, the only time you will see a real benefit is with huge batch jobs.

The 166 MHz overclock is interesting as many people are swooning over 200 MHz BLCK speed and 4.0++ GHz speeds, but I don't know what their CPU looked like after a week or two.

Well, I'm all about stability... if it's not stable, I don't bother. Getting over 200MHz might be easier on some motherboards than others, but I'm confident our P6T Deluxe exhibits what will be common clocks. To hit 200MHz (I am not even sure if it's possible, but I'll try to check later), it would require a lot of voltage, and to me, that's not worth it. You are only going to push the CPU temperatures to their upper-limit, and that's not exactly healthy.

To me, 3.33GHz is a sweet clock, especially for the money. It in no way can be considered slow, especially given that it's faster than the QX9770... for ~$300. Hard to be upset with a result like that.

It would be great if you, or someone else, could make a table of possible stable overclocking parameters for popular CPUs like the 920, with comments about the dangers of over-voltages or over- heating and revised lifetimes.

I'd like to... and it's something I had in mind to do already, but other things have really sucked my time and made it difficult to buckle down and get one written. I'll do one as soon as possible. Generally speaking though, overclocking the 920 is a lot easier than the 965, simply thanks to the lack of ability to tweak a wide variety of settings. It will really just be a matter of increasing the BCLK... and maybe the QPI or CPU voltages if your board requires it. I'm running 3.6GHz right now with only 1.275V CPU though... so I really don't think adjusting voltages will even be necessary.

 

[DeathBooger]

I didn't check the temperatures clock-for-clock, but you're right... it's not going to be a huge issue. I do believe the i7 965 includes a more robust CPU cooler though, but I still don't think it will matter too much. After all, it's not as though you'll be pushing the CPU 100% constantly... I just can't see temperatures becoming a problem whatsoever.

I'll probably see what my temperatures end up being and then decide to invest in a better cooler. Thanks for all the input. You've helped me a lot.

My last concern is my current PSU. It's an older OCZ Powerstream 520w that's good for 33A on the 12v rail. My current CPU has a TDP of 110w, which is only 20w less than the Core i7 920. I think I'll be okay, even with the overclocking.

 

[marchello - DK]

Different profiles..

I didn't check the temperatures clock-for-clock, but you're right... it's not going to be a huge issue. I do believe the i7 965 includes a more robust CPU cooler though, but I still don't think it will matter too much. After all, it's not as though you'll be pushing the CPU 100% constantly... I just can't see temperatures becoming a problem whatsoever.

I can assuredly say also that anything above 166MHz Base Clock is going to be sketchy. I tried to get the CPU to boot at 3.8GHz, and it just wasn't happening with reasonable voltages. Right now, I'm running 180x20 (3.6GHz) and it's rock-stable once again, both through 3DMark and the CPU stress test. Temperatures are 10°C higher than what they were with the 3.33GHz overclock.

I should also mention that the room temperature here is higher to begin with, so if you are in a room that hovers around 70°F, then you are automatically going to see much lower temperatures than me.



Well, as seen in the article, I don't think DDR3-1600 speeds are important at all, unless you happen use Adobe Lightroom or other image manipulation applications often. Even then, the only time you will see a real benefit is with huge batch jobs.



Well, I'm all about stability... if it's not stable, I don't bother. Getting over 200MHz might be easier on some motherboards than others, but I'm confident our P6T Deluxe exhibits what will be common clocks. To hit 200MHz (I am not even sure if it's possible, but I'll try to check later), it would require a lot of voltage, and to me, that's not worth it. You are only going to push the CPU temperatures to their upper-limit, and that's not exactly healthy.

To me, 3.33GHz is a sweet clock, especially for the money. It in no way can be considered slow, especially given that it's faster than the QX9770... for ~$300. Hard to be upset with a result like that.



I'd like to... and it's something I had in mind to do already, but other things have really sucked my time and made it difficult to buckle down and get one written. I'll do one as soon as possible. Generally speaking though, overclocking the 920 is a lot easier than the 965, simply thanks to the lack of ability to tweak a wide variety of settings. It will really just be a matter of increasing the BCLK... and maybe the QPI or CPU voltages if your board requires it. I'm running 3.6GHz right now with only 1.275V CPU though... so I really don't think adjusting voltages will even be necessary.

For ASUS P6T Deluxe u got the choice between different setups in the "AI tweaker - BIOS". My question is, is it possible to just adjust the profile from AUTO to D.O.C.P or XMP and then the BIOS find out the best optimized QPI, Vcore etc within the limit of what is stable or acceptable for not burning the cpu / reducing the lifetime? I mean u can actually have these options and read in the manual for the P6T board that if u have 1600 mhz ram u can set the profile to XMP.

 

[Rob Williams]

For ASUS P6T Deluxe u got the choice between different setups in the "AI tweaker - BIOS". My question is, is it possible to just adjust the profile from AUTO to D.O.C.P or XMP and then the BIOS find out the best optimized QPI, Vcore etc within the limit of what is stable or acceptable for not burning the cpu / reducing the lifetime? I mean u can actually have these options and read in the manual for the P6T board that if u have 1600 mhz ram u can set the profile to XMP.

No, the XMP profile doesn't matter when the multipliers are locked. On the Core i7 920 ( I can't speak on the 940 ), the memory multipliers enabled are 6x and 8x. With a Base Clock of 133MHz, the maximum memory frequency that can be achieved is 1066MHz. The XMP isn't a special case... it's just memory profiles. If the multipliers are locked, their locked.

The only way to increase the memory speed is to increase the Base Block, that's it. I went on to further overclock yesterday and found 180MHz to be completely stable on the P6T. That equates to a DDR3 speed of 1440MHz... not too shabby. It's not quite DDR3-1600, but it's far from being a wimpy frequency.

 

[marchello - DK]

No, the XMP profile doesn't matter when the multipliers are locked. On the Core i7 920 ( I can't speak on the 940 ), the memory multipliers enabled are 6x and 8x. With a Base Clock of 133MHz, the maximum memory frequency that can be achieved is 1066MHz. The XMP isn't a special case... it's just memory profiles. If the multipliers are locked, their locked.

The only way to increase the memory speed is to increase the Base Block, that's it. I went on to further overclock yesterday and found 180MHz to be completely stable on the P6T. That equates to a DDR3 speed of 1440MHz... not too shabby. It's not quite DDR3-1600, but it's far from being a wimpy frequency.

Well first of all i can say that the 940 does only have the 6x and 8x multipliers as the 920. As I see it, the 940 is waste of money, as its kind of a OC'ed version of the 920. Thanks for the reply. The conlusion must be then, that if got 1600 mhz memory u need to manually overclock the base clock within the stable limit.

okay 180 is high but good know its stable. Btw good test u made and for those which is interested in more info about the ram and oc u can check this page: http://www.tomshardware.com/reviews/Intel-Core-i7-Nehalem,2057-8.html

 

[Stu]

No, the XMP profile doesn't matter when the multipliers are locked. On the Core i7 920 ( I can't speak on the 940 ), the memory multipliers enabled are 6x and 8x. With a Base Clock of 133MHz, the maximum memory frequency that can be achieved is 1066MHz. The XMP isn't a special case... it's just memory profiles. If the multipliers are locked, their locked.

The only way to increase the memory speed is to increase the Base Block, that's it. I went on to further overclock yesterday and found 180MHz to be completely stable on the P6T. That equates to a DDR3 speed of 1440MHz... not too shabby. It's not quite DDR3-1600, but it's far from being a wimpy frequency.

Good article! I have two questions though...

1) Your testing results show little difference between 3GB and 6GB, suggesting that 3GB is sufficient... do you believe this to be true in real world usage when multi-tasking and with background programs (anti-virus, etc) running in Vista (rather than only having the benchmark software running)?

2) The results and your comments indicate that 1600MHz memory is a waste, and that 1333MHz would be a better choice due to price. However, when it comes to overclocking, is it better to get 1600MHz memory? You, and many others, have clocked your 920 to 3.6-3.8 GHz with the BCLK at 180 which "equates to a DDR3 speed of 1440MHz"... is DDR3-1333 guaranteed to support this BCLK frequency?