Yonah (microprocessor)

Yonah was the code name for (the core of) Intel's first generation of 65 nm process mobile microprocessors, based on the Banias/Dothan-core Pentium M microarchitecture. SIMD performance has been improved through the addition of SSE3 instructions and improvements to SSE and SSE2 implementations, while integer performance decreased slightly due to higher latency cache. Additionally, Yonah includes support for the NX bit.

Models and brand names

The Intel Core Duo brand refers to a low-power (less than 25 watts) dual-core microprocessor, which offered lower power operation than the competing AMD Opteron 260 and 860 HE at 55 watts. Core Duo was released on 5 January 2006, with the other components of the Napa platform. It was the first Intel processor to be used in Apple Macintosh products (although the Apple Developer Transition Kit machines, non-production units distributed to some developers, used Pentium 4 processors).^[1]

There were two variants and one derivative of the Yonah, which did not bear the "Intel Core" brand name. A dual-core (server) derivative, code-named Sossaman, was released on 14 March 2006 as the Xeon (branded) LV (low-voltage). The Sossaman differed from the Yonah only in its support for dual-socket configurations (two CPUs providing a total of four cores per motherboard, like AMD Quad FX), and implementation of 36-bit memory addressing (PAE mode). A single-core variant, code-named Yonah-1024, was released as the Celeron (branded) M 400 series CPUs. It was largely identical to the Core Solo branded Yonah, except that it only had half the L2 cache and did not support SpeedStep and Intel VT-x. Another dual-core variant of Yonah was branded as Pentium Dual-Core T2060, T2080, and T2130 mobile CPUs with Intel VT-x support.^[2]

Technical specifications

Core Duo contains 151 million transistors, including the shared 2 MB L2 cache. Yonah's execution core contains a 12-stage pipeline, forecast to eventually be able to run at a maximum frequency of 2.33–2.50 GHz. The communication between the L2 cache and both execution cores is handled by a bus unit controller through arbitration, which reduces cache coherency traffic over the FSB, at the expense of raising the core-to-L2 latency from 10 clock cycles (in the Dothan Pentium M) to 14 clock cycles. The increase in clock frequency offsets the impact of the increased clock cycle latency. The power management components of the core features improved grained thermal control, as well as independent scaling of power between the two cores, resulting in very efficient management of power.

Core processors communicate with the system chipset over a 667 MT/s front side bus (FSB), up from 533 MT/s used by the fastest Pentium M. T2050 & T2250 have also appeared in OEM systems as a low-cost option with a lower 533 MT/s FSB and no Intel VT-x.

Yonah is supported by the 945GM, 945PM, 945GT, 965GM, 965PM, and 965GT system chipsets. Core Duo and Core Solo use Socket M, but due to pin arrangement and new chipset functions are not compatible with any previous Pentium M motherboard.

Contrary to early reports, the Intel Core Duo supports Intel VT-x x86 virtualization, except in the T2300E model and proprietary T2050/T2150/T2250 mounted by OEMs (cf. the Intel Centrino Duo Mobile Technology Performance Brief and Intel's Processor Number Feature Table). The Intel Pentium Dual Core processors do not have this feature.^[3] However some vendors (including HP) chose to disable this feature,^[4][5] with others making it available through a BIOS option.^[6]

The T2300E was later introduced as a replacement for the T2300. It has dropped support for Intel VT-x. Early Intel specifications mistakenly claimed a halving of the Thermal Design Power.

Intel 64 (Intel's x86-64 implementation) is not supported by Yonah. However, Intel 64 support is integrated in Yonah's successor, the mobile version of Core 2, code-named Merom.

Advantages and shortcomings

The Duo version of Intel Core (Yonah) includes two computational cores, providing performance per watt almost as good as any previous single core Intel processors. In battery-operated devices such as notebook computers, this translates to getting as much total work done per battery charge as with older computers, although the same total work may be done faster. When parallel computations and multiprocessing are able to utilize both cores, the Intel Core Duo delivers much higher peak speed compared to the single-core chips previously available for mobile devices.

The shortcomings of Intel Core (Yonah) are:

• The same or even slightly worse performance per watt in single threaded or non-parallel applications compared to its predecessor.
• 32-bit architecture; see the Intel Core 2 successor, which is a 64-bit processor.
• High memory latency due to the lack of on-die memory controller (further aggravated by system-chipset's use of DDR2 SDRAM)
• Limited floating-point unit (multiply/divide) throughput for non-parallel computations or single-threaded processes; this is due to the smaller number of floating-point units in each CPU core compared to some previous designs.

The Yonah platform requires all main-memory transactions to pass through the northbridge of the chipset, increasing latency compared to the AMD's Turion platform. However, application tests showed Intel Core's L2-cache system is quite effective at overcoming main-memory latency; despite this limitation, Intel Core (Yonah) sometimes managed to outperform AMD's Turion.

The Sossaman processor for servers, which is based on Yonah, also lacks Intel 64-bit support. For the server market, this had severe consequences, since all major server operating systems already supported x86-64, and Microsoft Exchange Server 2007 requires a 64-bit processor to run.

According to Mobile Roadmaps from 2005, Intel's Yonah project originally focused more on reducing the power consumption of its P6-based Pentium M processor and aimed to reduce it by 50% for Intel Core (Yonah). Intel continued recommending the NetBurst-based Mobile Pentium 4 processors for high performance applications (although these were less power efficient and gave off significantly more heat) until the Yonah project succeeded in extracting higher performance from its lower-power-consumption design. The Intel Core Duo's inclusion of two highly efficient cores on one chip can provide better performance than a Mobile Pentium 4 core, and with much better power-efficiency. Intel no longer recommends its Mobile Pentium 4 processors for mobile devices as they are outdated.

On July 27, 2006, Intel's Core 2 processors were released. By Q2 2007, Intel expected 90% of its laptop CPU production to be converted to the heavily revised Intel Core 2 processors. The original Intel Core (Yonah) product had an unusually short lifespan as a stepping stone to the 64-bit Intel Core 2.

See also

• Intel Core
• Merom
• Centrino
• List of Intel Core microprocessors

References

External links

• Intel Core Duo Web page
• Intel Core Solo Web page
• Processor comparison table
• Intel Core technical specifications
• techPowerUp! CPU Database
• Tested against AMD's 64 X2 line and Intel's own Pentium M
• Intel Centrino Duo Mobile Technology papers