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Overclocking Intel’s Xeon E5620: Quad-Core 32 nm At 4+ GHz

The Contenders

Xeon E5620 ($384)

Intel Xeon E5620
Cores/Threads4/8
Stock Clock Rate2.4 GHz
Max. Turbo Boost Clock Rate2.66 GHz
Shared L3 Cache12 MB
Clock Multiplier/Max. Multiplier18/19
QPI Speed5.86 GT/s
Lithography32 nm Westmere-EP
Max. TDP80 W
VID Voltage Range.75-1.35 V
Memory SupportDDR3-800/1066
Price$384

A 211 MHz BCLK and 19x multiplier equals 4 GHz—a frequency that Intel’s 2.4 GHz Xeon E5620 has absolutely no trouble sustaining. A DDR3-1691 data rate falls well under our kit’s ceiling. So, I’m decidedly not worried about this configuration’s long-term prospects.

I know for a fact this chip could handle up to 4.2 GHz without breaking a sweat. The decision to use 4 GHz was based solely on the limitations of the other CPUs being tested.

Hitting those clocks only required marginal alterations. The CPU voltage was set to 1.35 V, its QPI/DRAM core voltage matched at 1.35 V, and the IOH voltage was nudged up ever so slightly to 1.258 V.

Core i7-970 ($879)

Intel Core i7-970
Cores/Threads6/12
Stock Clock Rate3.2 GHz
Max. Turbo Boost Clock Rate3.46 GHz
Shared L3 Cache12 MB
Clock Multiplier/Max. Multiplier24/25
QPI Speed4.8 GT/s
Lithography32 nm Gulftown
Max. TDP130 W
VID Voltage Range.80-1.375 V
Memory SupportDDR3-800/1066
Price$879

It’s a little unfair to include a processor that costs more than twice as much, but I wanted to show you what the cheapest desktop Core i7 based on the Gulftown design could do in comparison to the Xeon. This chip boasts six cores, but sports the same 12 MB of shared L3 cache.

Not surprisingly, the 3.2 GHz i7-970 overclocks well. Its 24x multiplier means you don’t have to push very hard for a 4 GHz overclock. Simply set the BCLK to a 160 MHz and increment the multiplier to 25x (the highest ratio this chip supports). We again use a 1.35 V CPU voltage setting, but leave the other voltages at their defaults, since we’re not pushing other clock rates very hard.

Greater than 4 GHz overclocks are also possible with this chip. But it’s hard to talk value when there’s an almost $900 CPU factored into the equation.

Core i7-930 ($284)

Intel Core i7-930
Cores/Threads4/8
Stock Clock Rate2.8 GHz
Max. Turbo Boost Clock Rate3.06 GHz
Shared L3 Cache8 MB
Clock Multiplier/Max. Multiplier21/22
QPI Speed4.8 GT/s
Lithography45 nm Bloomfield
Max. TDP130 W
VID Voltage Range.80-1.375 V
Memory SupportDDR3-800/1066
Price$284

Yes, yes, I know. The Core i7-950 costs just $10 more and gives you a higher multiplier setting. That’s not a very big deal here, though. We know Asus’ Rampage III Formula is good well beyond 200 MHz, and the Core i7-930’s highest 22x ratio means we only need a 182 MHz BCLK setting to reach 4 GHz.  

Nevertheless, our Core i7-930 sample wasn’t as willing of an overclocker as I had hoped it would be, and neither was a retail version of the chip I bought on Newegg a couple of months ago. Tagging 4 GHz on this CPU meant riding the edge of stability, with a reduced 1.325 V CPU voltage setting that kept temperatures cresting an uncomfortable 95 degrees Celsius in Prime95. I wouldn’t be comfortable using this chip at 4 GHz for an extended period of time.

It’s also worth noting that this CPU inspired our choice of heatsink/fan. While the two 32 nm processors ran cool enough to work with our Thermalright Ultra 120 eXtreme, the i7-930 needed more in order to run stably at 4 GHz. So, I switched over to Noctua’s NH-D14.

  • intelx
    i wish it had higher multiplier it would of been a great processor to recommend than paying $10000 for the i7 970.
    Reply
  • JOSHSKORN
    I wonder if it's possible and also if it'd be useful to do a test of various server configurations for game hosting. Say for instance we want to build a game server and don't know what parts are necessary for the amount of players we want to support without investing too much into specifications we don't necessarily need. Like say I hosted a 64-player server of Battlefield or CoD or however the max amount of players are. Would a Core i7 be necessary or would a Dual-Core do the job with the same overall player experience? Would also want to consider other variables: memory, GPU. I realize results would also vary depending on the server location, its speed, and the player's location and speed, too, along with their system's specs.
    Reply
  • cangelini
    JOSHSKORNI wonder if it's possible and also if it'd be useful to do a test of various server configurations for game hosting. Say for instance we want to build a game server and don't know what parts are necessary for the amount of players we want to support without investing too much into specifications we don't necessarily need. Like say I hosted a 64-player server of Battlefield or CoD or however the max amount of players are. Would a Core i7 be necessary or would a Dual-Core do the job with the same overall player experience? Would also want to consider other variables: memory, GPU. I realize results would also vary depending on the server location, its speed, and the player's location and speed, too, along with their system's specs.
    Josh, if you have any ideas on testing, I'm all ears! We're currently working with Intel on server/workstation coverage (AMD has thus far been fairly unreceptive to seeing its Opteron processors tested).

    Regards,
    Chris
    Reply
  • You could setup a small network with very fast LAN speeds (10Gbps maybe?). You can test ping and responsiveness on the clients, and check CPU/memory usage on the server. Eliminating the bottleneck of the connection and testing many different games with dedicated servers one can actually get a good idea of what is needed to eliminate bottlenecks produced by the hardware itself.
    Reply
  • Moshu78
    Dear Chris,

    thank you for the review but your benchmarks prove that you were GPU-bottlenecked almost all time.
    Letme explain: i.e. Metro 2033 or Just Cause 2... the Xenon running at 2.4 GHz provided the same FPS as when it ran at 4 GHz. That means your GPU is the bottleneck since the increase in CPU speed therefore the increase in the number of frames sent to the GPU for processing each second does not produce any visible output increase... so the GPU has too much to process already.
    I also want to point out that enabling the AA and AF in CPU tests puts additional stress on the GPU therefore bottlenecking the system even more. It should be forbidden to do so... since your goal is to thest the CPU not the GPU.

    Please try (and not only you, there is more than 1 article at Tom's) so try to reconsider the testing methodology, what bottleneck means and how can you detect it and so on...

    Since the 480 bottlenecked most of the gaming results are useless except for seeing how many FPS does a GF480 provide in games, resolutions and with AA/AF. But that wasn't the point of the article.

    LE: missed the text under the graphs... seems you are aware of the issue. :) Still would like to see the CPU tests performed on more GPU muscle or on lower resolutions/older games. This way you'll be able to get to the real interesting part: where/when does the CPU bottleneck?
    Reply
  • Looks to me to be a pointless exercise. I have been running an i7-860 @ 4.05 Ghz and low temps for more than a year now so why pay for a motherboard that expensive plus the chip?
    Reply
  • Cryio
    I have a question. Maybe two. First: Since when Just Cause 2 is a DX11 game? I knew it was only DX10/10.1 . And even if it is , what are the differences between the DX10 and 11 versions?
    Reply
  • blibba
    Note: Higher clocked Xeons are available.
    Reply
  • omoronovo
    blibbaNote: Higher clocked Xeons are available.
    However, I'm sure everyone is aware of how sharply the price of Xeons rise above the lowest-of-the-low. I expect a Xeon capable of 4.5ghz (a good speed to aim for with a 32nm chip and good cooling), you would already be over the costs of purchasing a 970/980x/990x, especially considering how good a motherboard you would need to get - a Rampage III extreme is possibly one of the most expensive X58 boards on the market, offsetting most of the gains you'd get over a 45nm chip and a more wallet friendly board - such as the Gigabyte GA-X58A-UD3R.
    Reply
  • compton
    This is one of the best articles in some time. I went AMD with the advent of the Phenom IIs despite never owning or using them previously, and I didn't once long going back to Intel for my processor needs. But I think that may have changed with the excellent 32nm products. The 980X might be the cat's pajamas, but $1000 is too much unless you KNOW you need it (like 3x SLI 480s, or actual serious multithreaded workloads when TIME = $$$). The lowly i3 has seriously impressed the hell out of me for value/performance, heat, and price/performance. Now, this Xeon rears it's head. While still pricey in absolute terms, it is still a great value play. Intel has earned my business back with their SSDs -- now might be the time to get back in on their processors, even if Intel's content to keep this chip in the Xeon line. Thanks for the illumination.
    Reply