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Sorting Out Intel’s Core 2 Duo Mobile Processors - Past, Present, And What’s Coming

Anyone out there besides me find Intel's CPU nomenclature conventions confusing? Core 2 Duo; Merom; Santa Rosa; Penryn; Centrino; Montevina; Nehalem; and so on and so on, and aside from the Core 2 Duo designation, those are just Intel's mobile chips and platforms.

Incidentally, if you're curious about those Jewish-sounding development code-names for Intel's Core CPUs, the reason it that they are engineered by Intel's chip design team in Haifa, Israel. For example, "Merom" is a Hebrew word meaning a higher plane of existence or level of heaven. Intel's Centrino mobile platform code-name designations on the other hand - Carmel, Sonoma, Napa, Santa Rosa, Montevina, are references to names from California's wine district.

Intel's Core (2) (Duo) brands refer to the company's consumer 64-bit dual-core and quad-core CPUs with the venerable x86-64 instruction set, based on Intel's Core microarchitecture and derived from the 32-bit dual-core Yonah laptop processor that shipped in Apple's original MacBook Pro notebooks in 2006.

Core 2 was rolled out on July 27, 2006, offered in Core Solo (single-core), and Duo (dual-core) for notebooks (I'll be concentrating almost exclusively on notebook CPUs in this column).

The relevant notebook Core 2-branded CPUs have included "Merom" and "Penryn" (used in MacBooks and MacBook Pros). Penryn CPUs are used in the current models of these machines. Merom, officially released in July, 2006, and based on 65 nanometer (nm) chip technology, was a low power consumption variant of the Conroe desktop CPU, also offering improved 3D rendering and media encoding, and was the first Intel mobile processor to feature Intel 64 bit architecture. It has a thermal profile of 34 watts current draw, and was pin-compatible with the Napa motherboard architecture.

A second generation of Merom processors came along in 2007, with an 800 MHz front side bus on the fourth-generation Centrino Santa Rosa platform that replaced Napa. and also soon found their way into the MacBook and MacBook Pro families.

The next wave of Core 2 Duo notebook processors, incorporating Intel's new 45 nm chip technology is Penryn, Using a combination of new materials including hafnium-based high-k gate dielectrics and metal gates, and with roughly twice the density of Intel 65nm technology, Intel's 45nm manages to pack roughly twice the number of transistors into the same silicon space - more than 400 million transistors for dual-core processors and more than 800 million for quad-core. This facilitates including up to 50-percent greater L2 cache, combined with increased energy efficiency. Penryn also includes Intel's GMA X3100 graphics technology in the version used in the MacBook, and has a 35W thermal profile, about the same as Merom, but in real-world service, Penryn runs somewhat cooler.

Intel is also building an as-yet Apple-only Penryn CPU with a clock speed of 3.06 GHz, a 1066 MHz Front Side Bus, and 6 MB shared L2 Cache available so far only in the most recent iMac revision.

So what are Centrino and Montevina?

Centrino is platform-marketing brand rather than a chip family per-se, and refers to a CPU, mainboard chipset and wireless network interface combination for notebook computers. The Centrino nomenclature has never been used by Apple, since the platform bundles and feature sets tend to be Windows-oriented. For example, OS X is not optimized to take advantage of Santa Rosa's "Robson" NAND flash-memory caching branded "Intel Turbo Memory." Computer makers like Apple that only use the respective CPU and chipset are authorized to use other Intel branding, such as Core 2 Duo.

Napa, Santa Rosa, and the forthcoming Montevina are all Centrino platform development code name designations.

Montevina, originally projected for release last week, but recently pushed back to at least mid-July and maybe August, will be the fifth-generation Centrino platform, dubbed Centrino 2 to help avoid confusion with earlier Centrino platforms. Montevina will support second-generation Penryn CPUs, and is slated to deliver enhanced processor performance for faster multitasking, high-bandwidth Wi-Fi (802.11agn) and for the first time, an optional integrated WiMAX/Wi-Fi module, and well as more advanced power-saving technology to help it run cooler with longer battery life.

The second-generation Core 2 Duo Penryn 45nm CPU will use the 1066 MT/s front side bus pioneered in the "iMac special" 3.06 GHz chip, and be offered in clock speeds ranging from 2.26 GHz to 3.06 GHz. It remains to be seen if the higher-speed Penryn 2s make it into the MacBook Pro. Penryn 2 is projected to have a thermal profile of no more than 29 watts, compared to Merom's and first-generation Penryn's 34 watt power draw, which should result in welcome cooler and longer running. MacBook purchasers can look forward to Intel's GMA X4500 integrated graphics technology in Penryn 2, clocked at 533/640MHz and containing ten unified shaders, up from the eight provided by Penryn 1's GMA X3100 graphics support system.

Looking farther ahead, the sixth-generation Centrino platform is being developed under the code-name "Calpella" and projected for release in Q3-4, 2009 with second-generation Nehalem processors - Nehalem being the next family of Core 2 Duo 45 nm CPUs.

The Nehalem microarchitecture represents the next step in processor energy efficiency, performance, and dynamic scalability, and has been designed from scratch to take advantage of Intel's hafnium-based 45nm hi-k metal gate silicon technology, Nehalem will also be the first Intel CPU to incorporate proprietary QuickPath technology offering what Intel calls performance "on-demand." and support for 2-8+ cores and up to 16+ threads with simultaneous multi-threading (SMT), and scalable cache sizes, system interconnects, and integrated memory controllers.

Simultaneous multi-threading brings high-performance applications into mainstream computing with 1-16+ threads optimized for new generation multi-core processor architecture. Scalable shared memory of Intel QuickPath technology features memory distributed to each processor with integrated memory controllers and high-speed point-to-point interconnects. Intel QuickPath Interconnect uses up to 6.4 Gigatranfers/second links, delivering up to 25 Gigabytes/second (GB/s) of total bandwidth. That’s up to 300 percent greater than any other interconnect solution currently in use. Multi-level shared cache improves performance and efficiency by reducing latency to frequently used data.

Applying Intel's "Tick-Tock" CPU development metaphor, Nehalem's microarchitecture marks the second step (a “tock”) to Penryn's "tick" in delivering a new process technology (tick) or an entirely new microarchitecture (tock) each year. The first Nehalem-based processors are projected for release in the latter part of 2008,

Intel’s 45nm Hi-k silicon process technology increases transistor switching speeds to enable higher core and bus clock frequencies and thus more performance in the same power and thermal profile, rather than just cranking out ever higher clock speeds and with commensurate energy demands and heat production. The objective is to achieve more within the same power consumption envelope or even reduced power demand. Nehalem will includes the ability to process up to four instructions per clock cycle on a sustained basis compared to just three instructions per clock cycle or less processed by other processors.

Other advances in Nehalem are to include simultaneous multi-threading for enabling a more energy-efficient ways of increasing performance for multi-threaded workloads, superior multi-level cache, including an inclusive shared L3 cache that can be up to 8 MB in size, more sophisticated microarchitecture facilitating two to three times more peak bandwidth and up to four times more realized bandwidth, performance-enhanced dynamic power management, and a higher-performance integrated graphics engine, and much much more.

Anandtech's Anand Shimpi recently got his hands on an actual Nehalem prototype. The motherboard it was running on was more than a bit dodgy, but Anand was able to form some favorable impressions notwithstanding. He notes, encouragingly, that "the CPUs are quite mature and are running extremely cool (surprisingly cool actually), their clock speeds are being artificially limited by Intel in order to avoid putting all cards on the table at this time."

Nehalem is not pin-compatible with Penryn, requiring a larger socket and more pins, and the the CPU itself is substantially bigger.

Performance, even with the deliberately detuned prototype chip and unoptimized motherboard was impressive, says Shimpi. "Clock for clock, Nehalem is nearly 28% faster than Penryn in our DivX test. Even better is when you put this performance in perspective: at 2.66 GHz Nehalem is faster than the fastest Penryn available today the Core 2 Extreme QX9770 running at 3.2GHz..... Encoding performance here went through the roof with Nehalem: a clock for clock boost of 44%," and despite "a 20 - 50% increase in performance, total system power consumption only went up by 10%..... We've been told to expect a 20 - 30% overall advantage over Penryn and it looks like Intel is on track to delivering just that in Q4."

You can read the full report visit here:
http://www.anandtech.com/cpuchipsets/intel/showdoc.aspx?i=3326&p=1

So, what does this all mean to you as an Apple 'Book user? Well, Nehalem is shaping up to be a honey of a notebook processor when it arrives, but that won't be until late 2009 if current projections hold, and in the meantime, the current Penryn CPUs are no slouch, although if you're not in any particular hurry to upgrade your system it might be worthwhile to hold off until the second-gen. Penryns debut with the Montevina/Centrino 2 rollout - the CPUs probably finding their way into MacBooks sometime in Q3 2008.


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cmoore@macopinion.com


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