Intel's LGA1156 and Lynnfield core

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Lynnfield LGA1156

September 7, 2009 by Lawrence Lee

Product Intel Core i7-870
LGA1156 Processor
Intel Core i5-750
LGA1156 Processor
Manufacturer Intel Intel
MSRP US$555 US$199

Intel's LGA775 socket started off in 2004 as a pariah for most PC hardware enthusiasts. Back then Intel was still knee-deep in its Netburst CPU architecture with Pentium 4s based on the hot, inefficient Prescott core. At about the same time, AMD launched Athlon 64. which was greeted with rave reviews and catapulted AMD ahead of Intel, but not just for a brief stretch. In a stunning turn of events, AMD, the perpetual underdog, would go on to push and stay ahead of Intel in performance and value for an unprecedented two years.

In 2006. however, Intel struck back, dumping Netburst and emerging to retake the performance crown with the Core and Core 2 architectures. The new processors retained the same LGA775 packaging, though in reality Core 2 required new chipsets and motherboards. Still, Intel had acquitted itself nicely and LGA775 will likely be thought of favorably in the future. Unfortunately all bad-turned-good things must eventually come to an end — the new LGA1156 socket now takes its place as Intel's value desktop platform, the Robin to LGA1366's Batman.


Simplified chipset block diagram. LGA775 on the left, LGA1156 on the right.


P55 Express chipset: block diagram. P55 provides all the usual goodies including a whopping 14 USB ports and 8 PCI Express 1x lanes.

LGA1366 represented a big upgrade in Intel's core architecture. Nehalem processors brought small changes like the reintroduction of Hyper-threading and a little free overclocking via Turbo Boost, but also drastic improvements including the addition of an integrated memory controller and the fast QPI interface connecting the controller to the Northbridge. The new LGA1156 processor, codenamed Lynnfield, takes mostly after Nehalem, but is designed to function with only one chipset. Lynnfield houses an integrated PCI Express controller, while the rest of the Northbridge's duties has been combined with those of the Southbridge into a single chip: the Platform Controller Hub. The PCH is connected to the processor via a DMI interface rather than QPI. Taking out a middleman is always good for efficiency. Lynnfield also lacks a triple channel memory controller — LGA1156 users must settle for dual.


Our Core i7-870 engineering sample.

LGA1156 processors will be branded Core i3, i5, and i7 depending on the number of cores, clock speeds, and features. The first Lynnfield chips released are the Core i7-870, i7-860, and i5-750, clocked at 2.93, 2.80, and 2.66 GHz respectively. They all have the same amount of cache and 95W thermal envelope, but the i5's are not equipped with hyper-threading, so the operating system can use a maximum of 4 threads rather than 8. i5 also lacks the VT-d feature which gives virtual machines the ability to directly access peripherals on their host. Turbo Boost has been ramped up as well. i5 clock speeds can be boosted an additional 533 MHz while i7 gets a maximum bump of 667 MHz.

Comparison Table: High-end Quad Core Desktop Processors (09/2009)
Platform
Model
Clock Speed
Total L2 Cache
Total L3 Cache
TDP
Street Price
LGA1366
i7-975 EE
3.33 GHz
1MB
8MB
130W
$1000
i7-950
3.06 GHz
$570
i7-920
2.66 GHz
$280
LGA1156
i7-870
2.93 GHz
1MB
8MB
95W
$555*
i7-860
2.80 GHz
$285*
i5-750
2.66 GHz
$199*
LGA775
QX9775
3.20 GHz
12MB
N/A
136W
$1550
Q9650
3.00 GHz
95W
$320
Q9550
2.83 GHz
$220
AM3
X4 965 BE
3.40 GHz
2MB
6MB
140W
$245
X4 955 BE
3.20 GHz
125W
$195
X4 945
3.00 GHz
125W
$170
* boxed price (1000 units)

At the $200 level, the i5-750 is set to compete directly with the Core 2 Quad Q9550 and Phenom II X4 955 BE. The i7-870's lofty price puts it in contention with the Nehalem based i7-950, though it's 133 MHz slower. Unless Lynnfield turns out to be superior to Nehalem clock-for-clock, LGA1156 motherboards will have be a fair bit cheaper to make the i7-870 a worthwhile purchase.


CPU-Z screenshot: Core i7-870.

Our Core i7-870 sample runs at 1.088V according the CPU-Z, which correlates to a BIOS setting of 1.1375V. Our i5-750 sample reads 1.200V which is the equivalent of 1.1625V in the BIOS.


CPU-Z screenshot:Core i5-750.



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