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Overclocking/Memory Scaling

Intel Core i7-975 Extreme And i7-950 Reviewed
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We wanted to test Intel’s Core i7-975 Extreme in two different ways: processor overclocking and memory scaling.

Heating up at 4.27 GHzHeating up at 4.27 GHz

The first part was easy, especially with an Extreme CPU. We used quick multiplier adjustments and found that 31x (4.12 GHz) was as fast as we could go stably. With voltages up to 1.385 V, we were able to get into Windows at 4.25 GHz, but at that point, it only takes a couple of minutes under Prime95 to push you into the 92-93 degree Celsius range, where blue screens are inevitable (this is with Thermalright’s Ultra 120 Extreme—naturally, the situation changes as you pursue more aggressive cooling). 

The i7-975 at 1.216VThe i7-975 at 1.216VThe i7-965 at 1.192VThe i7-965 at 1.192V

Once we backed off of 4.25 GHz, we were able to drop the voltage required for stability at 4.12 GHz all the way to 1.29 V. In order to switch things up a little bit, we also dropped the multiplier to 23x and hit 4.14 GHz with a 180 MHz Bclk (20 x anything over 200 MHz simply wasn’t cooperative). In either case, the result of our encoding test was exactly the same (1:05). Use multipliers if you can or Bclk if you’re not running an Extreme chip—what matters is that you hit your target.

Although the Core i7-975 Extreme sports the same 130W TDP as its predecessor, it's interesting that the new CPU runs a higher voltage by default (and despite the fact that it's a D0 stepping). See the CPU-Z screenshots up top for more.

OCZ was also kind enough to send over a set of its DDR3 PC3-17000 Blade modules specified for DDR3-2133 at 8-9-8. Given the extreme variance in price between mainstream and high-end DDR3 memory, we thought it’d be a good idea to quickly explore the benefits of loading up on memory running at those extreme speeds. In theory, low latencies are best in environments heavy on multi-tasking, where the fast timings enable quick bursts. Conversely, you’d suspect gobs of bandwidth to help most in data-intensive apps like video encode jobs.

It's worth noting, too, that achieving DDR3-2133 speeds necessitated bumping our QPI voltage to 1.75V (a substantial increase). This was required in order to run the cache/uncore at 4,266 MHz (twice memory speed). Even then, we were able to take a memory bandwidth reading but not complete a full run of MainConcept without stability issues. This is something that'll inevitably get worked out over time, we're sure. For now, OCZ considers the ICs that bin for these speeds to be the top 1% or so.

As you can see, there’s a huge difference in the bandwidth we’re moving using this triple-channel kit. The only truly strange result came from running at DDR3-800, where the memory controller switched off one channel, resulting in the lower-throughput result. Otherwise, the step-down is fairly even, so long as you maintain timings.

This is all well and good, of course, if you have modules able to do, say, DDR3-1066 at 5-4-4. But what if you want to compare an older DDR3-1066 kit running 9-9-9 to a lower-latency upgrade? We ran those numbers too, just to check, and came up with 19 GB/s (compared to 20.4 GB/s at 5-4-4).

For the most part, our real-world encoding batch demonstrates zero impact each step of the way. And even when we run the DDR3-1066/9-9-9 configuration, we come back with 1:19 as a result. At least in your average desktop environment, Intel’s Core i7 does not seem to be starved for throughput. We’ll spend some time exploring what exactly it does take to tax the micro-architecture’s memory subsystem in a couple of weeks.

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Top Comments
  • 22 Hide
    burnley14 , June 3, 2009 4:32 AM
    Good thing I didn't shell out for the 965 yesterday.

    Oh wait, I don't have unlimited cash, so I won't be shelling out for the 975 any time soon either . . .
  • 18 Hide
    smithereen , June 3, 2009 4:15 AM
    I've never seen anyone saying that the Phenom II is faster than any Core i7...
  • 15 Hide
    cruiseoveride , June 3, 2009 4:28 AM
    Doesn't make any difference with games
Other Comments
  • 18 Hide
    smithereen , June 3, 2009 4:15 AM
    I've never seen anyone saying that the Phenom II is faster than any Core i7...
  • 15 Hide
    cruiseoveride , June 3, 2009 4:28 AM
    Doesn't make any difference with games
  • 0 Hide
    cangelini , June 3, 2009 4:29 AM
    The i7's disadvantage in Far Cry 2 is well-known. That it gets beat in HAWX is something we only discovered this time around. In everything else, it's the faster CPU.
  • 5 Hide
    Tindytim , June 3, 2009 4:29 AM
    Are we going to see a price reduction in the 940 or the 965 that gives me any reason to purchase them over the 920?
  • 10 Hide
    cangelini , June 3, 2009 4:31 AM
    Not enough to warrant spending an extra $200 or more, in my opinion.
  • 22 Hide
    burnley14 , June 3, 2009 4:32 AM
    Good thing I didn't shell out for the 965 yesterday.

    Oh wait, I don't have unlimited cash, so I won't be shelling out for the 975 any time soon either . . .
  • 4 Hide
    Dustpuppy , June 3, 2009 4:40 AM
    Those game results look like you ran into serious GPU limits. As a result I think you may have been showing a difference in motherboards rather than processors on some of those tests. That does make it an interesting result in other ways though. It looks like the i7 boards have room to mature a little bit more relative to the older tech.
  • 3 Hide
    Summer Leigh Castle , June 3, 2009 4:43 AM
    Who said that AMD holds the crown in performance? I think any half witted enthusiast who hasn't been hiding underneath a rock for the past year knows that the i7 (and even the core 2 duo in some test) is king. I would hope that people who visit tomshardware or rather any tech website knows that in terms of highend power, AMD doesn't come close to Intel at all.
  • 3 Hide
    cangelini , June 3, 2009 4:54 AM
    DustpuppyThose game results look like you ran into serious GPU limits. As a result I think you may have been showing a difference in motherboards rather than processors on some of those tests. That does make it an interesting result in other ways though. It looks like the i7 boards have room to mature a little bit more relative to the older tech.


    Likely, yes. If you look back to this doozy of a benchmark-fest, you'll see it isn't under you add a second or third GTX 280 that i7 starts putting on some distance. Up until then, though, it's worth noting that the other two platforms (Core 2 and Phenom) are actually faster!
  • 8 Hide
    doomtomb , June 3, 2009 4:56 AM
    Really, any of the i7 processors besides the 920 seems like a waste because of the marginal performance increases for exponential price hikes. I was especially alarmed by the DDR3 memory results. There is the synthetic benchmark advantage of higher bandwidth at higher speeds but absolutely no difference across the board ranging from 1066 to 2133 in real world encoding or what not.

    Pretty absurd, I think I'd just stick with the 920 @ 3.8GHz and some affordable DDR3 1600MHz memory.
  • -1 Hide
    cadder , June 3, 2009 5:43 AM
    Do these higher end chips have higher overclock ability than the 920?
  • 4 Hide
    ohim , June 3, 2009 6:03 AM
    Summer Leigh CastleWho said that AMD holds the crown in performance? I think any half witted enthusiast who hasn't been hiding underneath a rock for the past year knows that the i7 (and even the core 2 duo in some test) is king. I would hope that people who visit tomshardware or rather any tech website knows that in terms of highend power, AMD doesn't come close to Intel at all.

    king to what ? a few nutcases that for 1 more fps will go and pay 700+ more $ ? even in the Video editing business let`s say .. nobody will go and buy those CPUs they don`t add to the $ and given the current crysis situation there won`t bee to many studios willing to throw out the window the price of a fully working station just to get a new CPU. For me now the Kings still are Intel`s i7 920 and AMD`s PII 955.
  • 6 Hide
    ravenware , June 3, 2009 6:31 AM
    Quote:
    If you spend enough time in our comments section, then you’re probably under the impression that AMD currently holds the performance crown and can do no wrong. I get it; AMD is the underdog and it’s hip to applaud competition. I'm certainly in favor of faster hardware, lower prices, and fair capitalism; those things benefit us all.


    WTF?

    I have yet to see anyone make such a claim and definitely not in mass.

    I have seen AMD Phenom II x3 720 dubbed the price to performance champion.
  • -1 Hide
    Tindytim , June 3, 2009 6:33 AM
    cadderDo these higher end chips have higher overclock ability than the 920?

    The 965 and 975 have an unlocked multiplier, so yes. By how much? I'm not sure.

    Is it going to be worth the $1000 price tag.
  • -1 Hide
    Sinj , June 3, 2009 6:36 AM
    Lol, this 975 only clocks 120mhz fast than my 920 D0 with no volts and it is much cooler at 60degrees at load
  • 0 Hide
    ohim , June 3, 2009 6:42 AM
    TindytimThe 965 and 975 have an unlocked multiplier, so yes. By how much? I'm not sure.Is it going to be worth the $1000 price tag.

    that`s what i was trying to point out in my previous comment but somebody out there instead of getting 3 x i7 920 they rather spend it all on only 1 cpu :)  so i put the question again king to what ? i rather have 3 computers powered by i7 920 than having only one i7 975, for an editing studio that means 3 ppl working at the same time doing 3 times much more work than 1 guy :)  These CPUs are not only for show an marketing to throw at ppl that they can realy crush AMD(but not in the games section where`s no logical reason to buy those) but very few ... too few will actualy buy those in the near future, and btw encoding is done with the guy afk from the pc you don`t sit at the PC ... i rather spend 700$ less and enjoy 2 more beers till my encoding is done ... at least this is how i see it.
  • -1 Hide
    cangelini , June 3, 2009 6:53 AM
    ravenwareWTF?I have yet to see anyone make such a claim and definitely not in mass.I have seen AMD Phenom II x3 720 dubbed the price to performance champion.


    I'm being facetious about the performance. But look at the comments in the most recent SBM. Three separate authors independently pick Intel platforms and suddenly there's a conspiracy going on ;-)
  • -1 Hide
    apache_lives , June 3, 2009 7:42 AM
    its stupid comparing this to a Phenom II when the Phenom II isnt priced anywhere near the same as the Intel part - the Core i5's will address this whole area and "compete" with with the Phenom II's etc as a mainstream part and as the Core 2 replacement.
  • 0 Hide
    anamaniac , June 3, 2009 8:05 AM
    It would be nice to know what Toms can crank the i7 875 up to with a decent water cooling setup. I just read an article on another site were a guy reached 2200+ ddr3 successfully and 4.6GHZ on a D0 i7 920.
    Some of us like to see what the limits are. :) 

    If the possible overclock gains are ignorable, if at all existent, I think the 920 will hopefully be my next baby if not a i5. The money saved on getting a 920 D0 over a 975 would pay for a sweet liquid cooling setup. Or maybe I should get a job again...
  • 2 Hide
    SpadeM , June 3, 2009 8:17 AM
    cangeliniI'm being facetious about the performance. But look at the comments in the most recent SBM. Three separate authors independently pick Intel platforms and suddenly there's a conspiracy going on ;-)


    I know that by now I sound like a broken record but u guys make the conspiracy possible. I mean look at the gaming benchmarks between Phenom 2 and i7 and Core... at first glance one would think "damn didn't know AMD was that fast" but that is a false impression. You guys made an article a couple of weeks ago stating that the i7+X58 doesn't play nice with Nvidia graphics, and you proved it. But despite that you keep on using a geforce 260 knowing it will perform lower when pair with the i7 (that is why on the LGA quad and Phenom 2 things look much better)
    And so you fuel the AMD vs Intel flame war that's going on. Please, make it clear once and for all, do a special article or something, write it with BIG LETTERS: 2 systems, i7 + nvidia and then a ati offering and a phenom system + nvidia and a ati offering.
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