Intel's LGA1156 and Lynnfield core

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Thermals

Core Temperatures
Test State
i7-870
i5-750
Stock
UV
Stock
UV
Core 0
56°C
49°C
54°C
47°C
Core 1
50°C
43°C
49°C
43°C
Core 2
56°C
49°C
54°C
48°C
Core 3
50°C
44°C
46°C
40°C
Average
53°C
46°C
51°C
45°C
Thermalright MUX-120 with stock fan @ 5.6V (900 RPM).
Ambient temperature: 22°C.
i7-870 undervolted to 1.025V stable (~1.1375V stock).
i5-750 undervolted to 1.0625V stable (~1.1625V stock).

In our open testbed, cooled by a Thermalright MUX-120 heatsink using the stock fan running at 900 RPM, the core temperatures (as reported by Core Temp and SpeedFan) were fairly low. Both processors averaged in the low 50's when placed under full load with Prime95. Undervolting cooled temperatures by 6-7°C. The heatsink barely felt warm during testing — it shouldn't be difficult to cool these processors quietly, but early adopters will have to wait for more cooling options to be released.

Motherboard Impressions

Our Intel DP55KG was a pre-production sample using the latest BIOS provided by Intel. It was quirky compared to most of the retail boards we've reviewed in the past. At first we used regular Corsair XMS3 memory, but the board refused to POST. We switched to XMS3 DHX, and it worked fine. After changing some minor settings in the BIOS, it again failed to POST, and required a BIOS reset. When we added a second stick of XMS3 DHX, the board again protested. In the end, we used two sticks of XMS3, which worked with a voltage increase, however, they would only function properly in the blue slots, not the black. Also, when we switched processors (even though we set the CPU settings to Automatic), we had to reset the BIOS once again. All in all, a rather frustrating experience. Luckily there is an error code display directly on the PCB. Other than the above problems, there were no stability issues and the board's VRM and chipset heatsink stayed lukewarm during testing.

The BIOS allowed for 3-pin and 4-pin control on three fan headers, though the CPU fan header generated an odd buzzing noise when used with the Thermalright MUX-120's stock PWM fan (swapping the fan or header resolved this issue). Incidentally, SpeedFan's current version, 4.39, does not support this board. The frequency and voltage options were liberal. You can change how much increase Turbo Boost provides, and you can vary the resulting speed depending on how many cores are in use. When you override the CPU voltage, you can leave SpeedStep on, so a lower idle CPU voltage is achieved when undervolting. VDroop can also be adjusted — the default setting is high which makes for lower power consumption. For more stable overclocking, it should be set to low.

FINAL THOUGHTS

Despite some hassles with a quirky motherboard, our experience with the new Lynnfield processors were mainly positive. They do not offer the kind of performance increase that LGA1366 brought to the table, but they bridge the gap between Core 2 Quads and the Bloomfield i7's. We were far more impressed with the energy efficiency of the i7-870 and i5-750 samples. Not only did they use less power than their LGA775 counterparts, they even managed to beat out the Q9550S, a high efficiency 65W part. As a bonus, they also displayed some undervolting potential. Cooling a Lynnfield processor should be a fairly trivial matter.

If you already have a fairly high speed quad core setup, there isn't any reason to jump ship to LGA1156. However, if you're aching to upgrade from a single or dual core system and energy efficiency is high on your wishlist, a Lynnfield may be just what the doctor ordered. From a pure performance/price standpoint, the i5-750 represents a solid value, giving stiff competition to the similarly priced, but higher-clocked Intel Q9550 and AMD X4 955 BE. The i7-870 on the other hand is LGA1156's flagship, and as such, is tagged with a heavy price premium. In most cases, the kind of money the i7-870 commands is better spent on a cheaper CPU with the savings distributed to other system components such as graphics cards and solid state drives.

CPU pricing is not the only thing to consider in regards to value — motherboards and memory are the other main factors. Solid information about LGA1156 motherboards is hard to come by with most rumors/speculation indicating a $100 price-point at the low-end, and upwards of $300 at the high-end. The street price for memory still favors DDR2 — 4GB of DDR3-1333 goes for $20 more than DDR2-800. Penny-pinchers may consider an AM3 quad core paired with a AM2+ motherboard a more palatable choice, especially if they've already invested in DDR2. A DDR2 powered Core 2 Quad system is somewhat less viable, given that LGA775 is nearing its end. In summary, LGA1156 looks like a natural and positive transition forward from 775.

Our thanks to Intel and Thermalright for the product samples used in this review.

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Intel Q9550S: A Greener Quad Core?
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Phenom II: AMD pulls closer
Intel Core i7: Nehalem Launched

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