The Contenders
Xeon E5620 ($384)
| Intel Xeon E5620 | |
|---|---|
| Cores/Threads | 4/8 |
| Stock Clock Rate | 2.4 GHz |
| Max. Turbo Boost Clock Rate | 2.66 GHz |
| Shared L3 Cache | 12 MB |
| Clock Multiplier/Max. Multiplier | 18/19 |
| QPI Speed | 5.86 GT/s |
| Lithography | 32 nm Westmere-EP |
| Max. TDP | 80 W |
| VID Voltage Range | .75-1.35 V |
| Memory Support | DDR3-800/1066 |
| 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/Threads | 6/12 |
| Stock Clock Rate | 3.2 GHz |
| Max. Turbo Boost Clock Rate | 3.46 GHz |
| Shared L3 Cache | 12 MB |
| Clock Multiplier/Max. Multiplier | 24/25 |
| QPI Speed | 4.8 GT/s |
| Lithography | 32 nm Gulftown |
| Max. TDP | 130 W |
| VID Voltage Range | .80-1.375 V |
| Memory Support | DDR3-800/1066 |
| 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/Threads | 4/8 |
| Stock Clock Rate | 2.8 GHz |
| Max. Turbo Boost Clock Rate | 3.06 GHz |
| Shared L3 Cache | 8 MB |
| Clock Multiplier/Max. Multiplier | 21/22 |
| QPI Speed | 4.8 GT/s |
| Lithography | 45 nm Bloomfield |
| Max. TDP | 130 W |
| VID Voltage Range | .80-1.375 V |
| Memory Support | DDR3-800/1066 |
| 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.
