Related articles

• With Core 2 Quad and Core 2 Duo, you had a general idea of what you were dealing with upfront. Adding a Q8000- or E7000-series designator wasn’t particularly descriptive, but at least there was one tangible identifier in there for the layman to digest. When Intel introduced Core i7 last year, the fact that there was only one Nehalem-based desktop family made it easy to say “Core i7—yeah, high-end stuff,” regardless of whether you were actually talking about the $300 i7-920 or the $1,000 i7-965. Now you have Core i5 and another strain of Core i7; at this point the nomenclature is just jargon for everyone except for the power users who live and breathe this stuff. Let’s break it down in a neat little table, though. Core i7 (LGA 1366)Core i7 (LGA 1156)Core i5Core 2 QuadProcessor InterfaceLGA 1366LGA 1156LGA 1156LGA 775Number of Cores4444Turbo BoostYesYesYesNoHyper-ThreadingYesYesNoNoL1 Cache32KB/32KB per core32KB/32KB per core32KB/32KB per core32KB/32KB per coreL2 Cache256KB per core256KB per core256KB per coreUp to 12MB sharedL3 Cache8MB shared8MB shared8MB sharedNoMemory Channels3222Max. Memory RateDDR3-1066DDR3-1333DDR3-1333DDR3-1600ChipsetX58P55P55X48Price$284-$999$285-$555$199$163-$316 As you can see, Core i7 for LGA 1366 remains the enthusiast-class offering, sporting the most PCI Express 2.0 connectivity via Intel’s X58 Express chipset, up to three available channels of DDR3 memory support, Intel’s first generation of Turbo Boost, and Hyper-Threading. Core i7 for LGA 1156 integrates the PCI Express connectivity (albeit 16 lanes instead of 36), sheds one memory channel, incorporates an updated implementation of Turbo Boost, and maintains Hyper-Threading support. Core i5 includes the same on-board PCI Express subsystem and dual-channel integrated memory controller. It employs Intel’s improved Turbo Boost (though it’s slightly less aggressive than i7’s). What it lacks, however, is Hyper-Threading—apparently a noteworthy-enough capability to turn an i7 into an i5. Of course, descending the stack also results in lower base clock rates. The Making Of A Core i5/i7 Architecturally, most of what you get in a Core i5 or Core i7 processor is borrowed from technology already found in Intel’s LGA 1366-based Core i7 and Xeon 3500-series processors. The Lynnfield die is different from Bloomfield though, estimated at 774 million transistors packed into 296 square millimeters (versus 731 million in 263 millimeters for the first Core i7s). More than 400 million of those transistors make up the CPU's cache. As with Bloomfield, Lynnfield is a monolithic design divided into four cores (execution pipelines, L1 data/instruction cache, TLBs) and the uncore (L3 cache, integrated PCI Express, the memory controller, QPI, and the PLLs). The power for these two “halves” remains separate, independently adjustable in your motherboard's BIOS. Each of the four cores retains its 32KB L1 data cache (still 8-way set-associative), 32KB L1 instruction cache (still 4-way set-associative), and 256KB L2 cache (you guessed it—still 8-way set associative). An inclusive 8MB L3 cache 16-way set-associative) should look familiar as well.  With nothing really new to report in the cores themselves, we move to the uncore, where Intel has added PCI Express 2.0 connectivity, axed a single memory channel, dropping the total to two, and altered QPI.

• The integrated PCI Express, two-channel memory controller, and tweaked QPI link are notable changes from Bloomfield to Lynnfield, but none are as story-altering as Intel’s latest version of Turbo Boost technology. You’ll remember from our Bloomfield analysis that Core i7-900-series CPUs feature a PCU (power control unit), an on-die controller with approximately the same number of transistors as a complete 486 processor. At regular intervals, the PCU samples temperature, current, power consumption, and operating system states. What does it do with this information? In the case of Bloomfield, which has a 130W TDP, the processor can almost completely shut off cores that are not in use by dropping them into C6, cutting consumption. Obviously, idle cores (those in C3 or C6) result in a larger gap between actual power use and the imposed maximum. So, in threaded workloads, where three or four of Bloomfield’s cores are working (but still under the PCU’s programmed limits), this feature called Turbo Boost increments the CPU’s clock ratio by one. Multiplied by a 133 MHz base clock, that’s an additional 133 MHz of free clock rate. With only one core active (in C0 or C1), Turbo Boost could take things up a second performance bin, adding 266 MHz to the chip’s standard clock. Now, back when the Core i7-975 Extreme launched, I observed that it was actually very rare to see two bins of Turbo Boost in practice, since Vista’s scheduler has a bad habit of bouncing threads from one core to another, keeping multiple cores in action. I was able to screenshot the 975 running at 3.6 GHz, but it only lasted a fraction of a second. In that case, two bins wouldn't be what I’d consider a tangible benefit. Fast forward to today. All three Core i5 and Core i7 CPUs now sport a 95W TDP (and an 89A ceiling), making the PCU’s power-policing duties even more critical. Adding further to the controller’s role is a more aggressive implementation of Turbo Boost. With three or four cores active, the Core i5-750 and Core i7-860 get a one-bin improvement each (the Core i7-870 gets two). But with only two cores active, all three models enjoy a four-bin (533 MHz) speed-up. And with one core active, the two Core i7s get five bins (667 MHz) so long as you’re still under 95W. Turbo Boost: Available Bins (Under TDP/A/Temp)Processor NumberFrequency4 Cores Active3 Cores Active2 Cores Active1 Core ActiveCore i7-8702.93 GHz2245Core i7-8602.8 GHz1145Core i5-7502.66 GHz1144Core i7-9753.33 GHz1112Core i7-9503.06 GHz1112Core i7-9202.66 GHz1122 At the end of the day, this is really the legacy of Lynnfield. In threaded environments, you see the benefit of a quad-core processor. In titles like WinZip, Lame, or iTunes—benchmarks we’ve seen time and time again favor higher-clocked dual-core chips—Lynnfield kicks into gear to serve up better single-threaded speed. In order to keep an even closer handle on consumption, the sampling rate of Lynnfield’s PCU is increased versus Bloomfield. Consequently, the new Core i5 and Core i7 processors can ramp voltage up or bring it back down more aggressively than Bloomfield-based CPUs, and thus react faster to a given single- or multi-threaded workload. It’s all fine-tuning really, but when you’re talking about switching between idle and active states, every little bit counts. Testing Turbo It’s actually really easy to see Turbo Boost in action, thanks to the TMonitor beta at cpuid.com. By simply assigning an application to a single processor core through Windows’ Task Manager, it’ll be constrained to that one CPU, realizing as much Turbo Boost acceleration as is available. Incidentally, this isn’t the best way to actually use a Core i5- or Core i7-based machine, as we realized better performance by default (even though iTunes looks to be jumping around between available cores). As you might expect from a technology that can “overclock” a Core i5-750 from 2.66 GHz to 3.2 GHz in single-threaded workloads, the performance potential is significant. Our upcoming benchmarks compare the new i5 and i7 processors against Bloomfield, Yorkfield, and AMD’s Deneb, but here you’ll see i5-750 with Turbo on and off under iTunes. The result is compelling, especially when you look at how the i5 does against the rest of the pack. Put the i5-750 ($199) up against the i7-920 ($279-ish) in single-threaded apps and you get even more interesting results. Turbo Boost is the “killer app” that’s going to allow these Lynnfield processors to beat out more expensive Bloomfield configurations in the right environments. Core i7 Coming Up Short With One Core Active? In trying to get the very most out of Turbo Boost, we did observe some interesting behavior with single-core scenarios. The Core i5-750 had no trouble realizing its four-bin boost, jumping from 2.66 GHz to 3.2 GHz in a number of workloads. However, as we observed in our Core i7-975 Extreme review, the Core i7-870 and Core i7-920 failed to reach their 3.6 GHz and 2.93 GHz peaks, respectively, unless you force the running program into a single core manually. Now, according to Intel, most applications that report clock rates rely on ACPI-based P-states, and are thus unable to correctly detect frequencies modified by Turbo Boost. But we’ve been assured that TMonitor does properly reflect the actual frequency on a per-core basis. Consequently, it’s more accurate to think of the Core i7-800s as receiving four bins with one core active and the Core i7-900s as getting one extra bin, rather than counting on five and two bins, respectively. See more products Intel Core i7 I7-920 Quad Core... Dell Home $349.99 ServerSupply.com $340.00 Apogee Source $305.25 Compuvest $311.46 ElectronicsPLUS $319.69

• In Theory: How Does Lynnfield's On-Die PCI Express Affect Gaming?

  We've had Intel's Core i5 in the lab now for almost three months, benchmarking, overclocking, and fiddling with a bundle of pre-production motherboards. Along the way, we've raised questions and sought answers. One of those questions was largely theoretical, but we wanted defensible backup anyway: does the on-die PCI Express connectivity integrated into Intel's Core i5 and Core i7 CPUs for LGA 1156 have any affect on gaming performance? All of these benchmarks were actually run before we even received a CPU sample from Intel. But because we knew we'd be running tests on the new i5 and i7 processors (and before we started interpreting data from those processors or their P55-based platform), it was important to figure out how much our gaming results would be affected by the CPUs themselves, with Turbo Boost and Hyper-Threading already serving as significant variables. Asking The Right Questions Knowing that these two new mainstream processor families incorporate 16 lanes of second-gen PCI Express on-die, yet tout CrossFire and SLI support, what happens to your frame rates when you run a single card in such a low-latency x16 interface? How about the effect of splitting that link into a pair of x8 connections? Will Core i5 handicap you right out of the gate with multi-card configurations? Just for a bit of perspective, remember that Intel's P45 chipset also divides 16 lanes into a pair of x8 links when two AMD-based cards are installed. Thus, we're comparing Core i5 to P45 here, in addition to X58 and AMD's 790GX (the former serving up two x16 links while running in CrossFire, and the latter delivering a x8/x8 split). Up until today, we’ve been all about Core i7-920 overclocked to somewhere around 4 GHz on an X58 motherboard with 6 GB of memory in a triple-channel arrangement. That’s a nearly-$600 proposition between the CPU, motherboard, and memory. If Core i5 can bring processor and motherboard prices down far enough, we’re guesstimating a price tag of $400-$425 with a drop to 4 GB of memory. Should Intel's new mainstream lineup proves fast enough, the ~$170 savings could translate to a “free” GeForce GTX 260 or Radeon HD 4870…so long as gaming performance is at least competitive with an LGA 1366-based Core i7, that is. On-Die PCIe: A New Design Cue As you likely already know, the Lynnfield design (on which the Core i5 and certain Core i7 processors center) includes 16 lanes of second-gen PCI Express. Why? Because the processor attaches to Intel’s P55 chipset via DMI (as opposed to Core i7’s single QPI link); there isn’t enough throughput between the two components for single-, much less dual-GPU communication. Of course, this opens the door to some interesting performance-oriented questions. Does the on-die PCI Express link reduce latencies enough to improve performance with a single card installed versus Core i7? Does splitting the 16-lane connection into a pair of x8s make enough of a difference to manifest itself in gaming benchmarks with two cards installed? How about the folks upgrading from Core 2 Quad machines, or those considering Phenom II as they wait to see what Core i5 will do? We’ve put together the hardware needed to answer those questions from a fairly high level. Remember, these benchmarks were run on pre-production hardware for the purpose of answering a largely academic question. Turbo Boost was disabled on the LGA 1366 platform, as were all of the power-saving processor technologies that might otherwise skew our look at frame rates. See more products Intel Core i7 I7-920 Quad Core... Dell Home $349.99 ServerSupply.com $340.00 Apogee Source $305.25 Compuvest $311.46 ElectronicsPLUS $319.69