3GB or 6GB with i7 920?

Stu

Stu

Stu

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I'm about to build an new rig based around an i7 920, and I am considering whether to get 3GB or 6GB of memory, as the price difference is obviously significant.

I'm pretty much decided that I need 1600Mhz memory to allow me to get a decent overclock.

I'm sold on the idea that 2GB is not enough with Vista, and that 4GB is the sweetspot for performance vs price for a dual channel setup, but what about for tri-channel.

I've read the article from Corsair covering this topic, but, despite their conclusions, I wasn't totally sold on the conclusion that 6GB was essential... sure, it's going to be better than 3GB, but when you consider price, you ask yourself if it is really necessary.

That said, I can see myself upgrading to 6GB in the future, as I expect this new rig to last at least 4 years... so, do I get 6GB now, or only get 3GB while the current prices and memory latencies are high, and then sell and upgrade later?
 
Stu said:
I'm pretty much decided that I need 1600Mhz memory to allow me to get a decent overclock.
Click to expand...

After making my statement above about 1600Mhz, I've just read an interesting article at Techgage... they show that there is virtually no difference in real world terms between 800 and 1600MHz with the i7 platform! :eek:

I might rethink my previous statement to save a few pennies... I need to do some research to find out how memory speed is linked to the processor speed for overclocking.
 
fornowagain said:
Did you see this thread?

Core i7 and Games, Memory Testing 6GB vs 3GB
Click to expand...

Thanks for the reference... I hadn't read this before, however, it discusses the same article by Corsair that I linked to above. After reading the other thread, I don't believe an independent consensus has been reached.

Regarding overclocking, I have discovered that the i7 uses 6x and 8x memory dividers. (Source: Tom's Hardware)

The 920 has a locked multi of 20. The highest BLCK I expect to hit is 200, which would give a CPU frequency of 4 GHz (this is very optimistic).
With a 8x memory multiplier, 8 x 200, DDR3-1600 would be required.
However, the 6x multiplier, 6 x 200, means that DDR3-1200 can support an overclock to 4 GHz; therefore DDR3-1333 should do the job. The memory is obviously running slower with the lower memory multiplier, however, the Techgage article indicates that this is not a real world issue.

The original question still remains, 3GB or 6GB?
 
I'm in the same boat as you. I haven't made up my mind yet, but I'm edging towards 6GB at 1333Mhz, and then running the 6x multiplier.
 
The retail 920/940 actually have more available memory multi than Toms indicates depending on the board. Although I'm aiming at the 1600 cas 8 area.

The multi on a Gigabyte UD5 + 920
Core = x12 - x20
Uncore = x12 - x48
Mem = x6 - x18
QPI = x36 - x48


 
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fornowagain said:
The retail 920/940 actually have more available memory multi than Toms indicates depending on the board. Although I'm aiming at the 1600 cas 8 area.

The multi on a Gigabyte UD5 + 920
Core = x12 - x20
Uncore = x12 - x48
Mem = x6 - x18
QPI = x36 - x48


Click to expand...

Are you sure that these images are from a system using a 920, and not an engineering sample or 965 running at 920 spec... I ask because the CPU multi appears to be unlocked in the second screenshot and I have read that the 940 and 965 have additional memory multipliers, but the 920 only has 6x and 8x.

That said, most people are hitting 3.6GHz with a 920, which means a 180 BLCK with the 20x CPU multi... using a 10x memory multi, DDR3-1800 would be required - this is definitely out of budget!!! :eek: Even higher memory multipliers are just insane. Unless a compromise is made on the CPU overclock, 6x and 8x memory multipliers are enough for me!
 
I've been going through the exact same motions for my i7 build and have come to the same conclusion, 6GB DDR3-1333MHZ with the 6x multiplier.

Can I also say this is probably been the most helpfull and informative thread I've read in a long time :)
 
Stu said:
Are you sure that these images are from a system using a 920, and not an engineering sample or 965 running at 920 spec... I ask because the CPU multi appears to be unlocked in the second screenshot and I have read that the 940 and 965 have additional memory multipliers, but the 920 only has 6x and 8x.

That said, most people are hitting 3.6GHz with a 920, which means a 180 BLCK with the 20x CPU multi... using a 10x memory multi, DDR3-1800 would be required - this is definitely out of budget!!! :eek: Even higher memory multipliers are just insane. Unless a compromise is made on the CPU overclock, 6x and 8x memory multipliers are enough for me!
Click to expand...

Yes I'm sure that's a retail 920. I've even asked a few owners to be certain. The 920 is the same as the 940 bar the cpu multiplier.

http://www.xtremesystems.org/forums/showthread.php?t=205779&page=7
http://www.xtremesystems.org/forums/showpost.php?p=3442796&postcount=293

Yes, but remember with the normal range of baseclock the higher memory multi's are needed for faster ram. The default 133x8 is a bit limiting, a x12 multi gets you into 1600Mhz with stock cpu speeds.

I agree though, with realistic max 200 BCLK then 1333Mhz is fine tbh.

166 x 8 = 1333MHz / 166 x 20 = 3333Mhz
200 x 6 = 1200MHz / 200 x 20 = 4000Mhz
220 x 6 = 1320MHz / 220 x 18 = 3960Mhz

200 x 8 = 1600MHz / 200 x 20 = 4000Mhz

Personally I went with 6Gb of the Corsair Dominator (TR3X6G1600C8D), but I got it cheap otherwise I wouldn't have bothered. I think the question that should be asked, is triple channel really needed? I'd bet that 2x2Gb would be fine for desktop/gaming rigs, performance within a percent or two and less stress on the uncore. They're pushing the low voltage stuff for the tri-channel. 3G's is out especially for 64bit users, so that leaves only 6Gb.
 
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I feel better that someone else agrees that DDR3-1333 should be enough... there's a bit of me that thinks I'm taking the soft option by not getting 1600, but with the price of x58 mobos, I shouldn't complain about saving £50 on the RAM by getting 1333.

Going back to the option of a 10 memory multiplier, lets assume DDR3-1600 (any higher is silly prices)... 1600 / 10 = 160 --> 160 BLCK x 20 CPU multi = 3.2GHz CPU frequency... I'm really hoping for more than 3.2!!! So 10x memory multi is not oin to be used by the typical overclocker.

I have seen that the MSI Eclipse offers 3, 4, 5, 6 and 7.

I think it comes down to this... the 6x and 8x multipliers offered on the Asus P6T (which I have my one on) give sufficient flexibility to support an overclock to 4GHz using DDR3-1333 or DDR-1600. Using DDR3-1600 means higher bandwidth and lower latency (see Techgage article), but the onboard memory controller setup provides so much bandwidth that real world applications have more than enough with the slower DDR3-1333.
 
Back to my original question :D, I'm thinking that 6GB is the way to go, and by choosing DDR3-1333 the price isn't so bad.
 
I'm looking at the 940, say it tops at 180 BCLK then x10 might get used. 1800Mhz won't make a fiddles difference in 24/7 usage, but it can help the odd bench along.

180 x 10 = 1800MHz / 180 x 22 = 3960Mhz

Stu said:
Back to my original question :D, I'm thinking that 6GB is the way to go, and by choosing DDR3-1333 the price isn't so bad.
Click to expand...
Which ones? Some of the early stuff will be rubbish with poor latencies, 1333Mhz cas 9 ain't that great. Some of that OCZ (OCZ3P1333LV6GK) 1333Mhz cas 7 looks nice.
 
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I'm thinking about the G.Skill 6GB 1333MHz kit. It's 9-9-9-24, but we've established that timings don't really matter with the i7. Also, it's rated as needing only 1.5v, so it might overclock well with a little more juice, letting me use the 8x memory multi or reduce the timings (even though I don't think it will make a difference :rolleyes: :D ). At £165, the price is much cheaper than DDR3-1600.
 
That's the exact same one I've pretty much settled on. Tis a shame I'm actualy going to be putting my build on hold. Completely forgot the weekly offers end and start on Wednesdays and as 70% of my build was in last weeks offers, the total price has now gone up by £100

Doh
 
Strife212 said:
The price of everything on the website has just gone up :/

Dire, was right on the edge of ordering an i7, don't think I will now :S
Click to expand...

yea I noticed that too...:mad: I have had an i7 chip, mobo and ram in the basket since monday, was almost gonna go for it, and over 5 days its has gone up twice, was just over 600, then to 638, then today its 649 lol.

Oh well, its just telling me to wait.
 
I have a set of 1333mhz ocz platinums but they overclock to 1680mhz at cas 8-7-7-20 using 1.64v. They might do more but I haven't really tried. Tested using memtest.
 
I also now have a OCZ Platinum 1333MHz 7-7-7-20 set, however, I haven't had time to fully test them yet.
 
Sorry to necro a thread but what was the conclusion?

Looking at the current prices it's either a slower 6 gig kit or a faster 3 gig kit. I read the various links etc.

I'm planning on getting a 920 and pushing it to around the 3.3-3.5GHz mark, is 6 worth the speed loss?
 
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