Nehalem (microarchitecture)

Intel Nehalem (microarchitecture)

Nehalem is the codename for an Intel processor microarchitecture., The first processor released with this architecturce is the desktop Core i7. Nehalem will be released in late 2008 for high-end desktop and dual-processor platforms and in Q4 2009 to Q1 2010 for mainstream desktop and mobile platforms. The microarchitecture is the successor to the Core microarchitecture.

Initial Nehalem processors use the 45 nm manufacturing methods from Penryn. A working system with two Nehalem processors was shown at Intel Developer Forum Fall 2007, and a large number of Nehalem systems were shown at Computex in June 2008.

The processor is named after the Nehalem River in Northwest Oregon, which is in turn named after the Nehalem Native American tribe in Oregon. The code name itself had been seen on the end of several roadmaps starting in 2000. At that stage it was supposed to be the latest evolution of the NetBurst architecture. Since the abandonment of NetBurst, the codename has been recycled and refers to a completely different project.

Technology

As described at Spring IDF 2008, Nehalem appears to incorporate the most significant new architectural changes to the x86 microarchitecture since the Pentium Pro debuted in 1995. Nehalem is highly scalable with different components for different tasks. Various sources have stated Nehalem's specification will have:

  • Two, four, or eight cores
  • From 45 nm move to 32 nm manufacturing process
  • Integrated memory controller supporting DDR3 SDRAM and between one and six memory channels
  • Integrated graphics processor (IGP) located off-die, but in the same CPU package
  • A new point-to-point processor interconnect, the Intel QuickPath Interconnect, replacing the legacy front side bus
  • Simultaneous multithreading by multiple cores and hyperthreading, which enables two threads per core. Simultaneous multithreading has not been present on a consumer Intel processor since 2006 with the Pentium 4 and Pentium XE.
  • Native (monolithic, i.e. all processor cores on a single die) quad- and octo-core (8) processors
  • The following caches:
    • 32 KB L1 instruction and 32 KB L1 data cache per core
    • 256 KB L2 cache per core
    • 2-3 MB L3 cache per core shared by all cores
  • 33% more in-flight micro-ops than Conroe
  • Second-level branch predictor and second-level Translation Lookaside Buffer
  • Modular blocks of components such as cores that can be added and subtracted for varying market segments

Event demonstrations at the Shanghai Intel Developer Forum showed A1 silicon Bloomfield-based Nehalem processors at IDF running at 3.2 GHz. This processor had 32 KB L1 instruction and 32 KB L1 data cache, 256 KB L2 cache per core, and 8 MB of shared L3 cache.

Performance and power improvements

It has been reported that Nehalem will have a focus on performance, which accounts for the increased core size. Compared to Penryn, Nehalem will have:

  • 1.1x to 1.25x the single-threaded performance or 1.2x to 2x the multithreaded performance at the same power level
  • 30% lower power usage for the same performance
  • According to a preview from AnandTech "expect a 20-30% overall advantage over Penryn with only a 10% increase in power usage. It looks like Intel is on track to delivering just that in Q4."
  • Core-wise, clock-for-clock, Nehalem will provide a 15%-20% increase in performance compared to Penryn.

PC Watch found that a Nehalem "Gainestown" processor has 1.6x the SPECint_rate2006 integer performance and 2.4x the SPECfp_rate_2006 floating-point performance of a 3.0 GHz Xeon X5365 "Clovertown" quad-core processor.

A 2.93 GHz Nehalem "Bloomfield" system has been used to run a 3DMark Vantage benchmark and gave a CPU score of 17,966. The 2.66 GHz variant scores 16,294. A 2.4 GHz Core 2 Duo E6600 scores 4,300.

AnandTech tested the Intel QuickPath Interconnect (4.8 GT/s version) and found the copy bandwidth using triple-channel 1066 MHz DDR3 was 12.0 GB/s. A 3.0 GHz Core 2 Quad system using dual-channel 1066 MHz DDR3 achieved 6.9 GB/s.

Overclocking will be possible with Bloomfield processors and the X58 chipset. The Lynnfield and Havendale processors will use a PCH removing the need for a northbridge chipset.

Variants

Nehalem will come in variants for servers, desktops, and notebooks. The four-socket server CPU is codenamed Beckton, the two-socket server CPU is codenamed Gainestown, and the single-socket desktop CPU is codenamed Bloomfield. Server processors will support registered DDR3.

Seven code names have been associated with the Nehalem microarchitecture in a PC Watch article. These include two server processors, three desktop processors, and two mobile processors. The server processor, Beckton, will have 44 bits of physical memory address and 48 bits of virtual memory address. The mainstream and value processor, Havendale, will have a FDI bus. It has been said that Havendale will have two different IGP versions and at least six different parts, possibly six different frequencies. It will also replace both dual-core and quad-core Penryn CPUs. Intel has confirmed that there will be at least four different variants of Nehalem CPUs. One variant is Core i7 while two others are slated for 2009 as dual- and quad-core.

Codename Market Segment Process Cores (Threads) Speed Price Cache Memory Controller Bus Interface GPU TDP Socket Release Period
Westmere DP server 32 nm 4 (8) and/or 6 (12) 256 KB L2/core
12 MB shared L3
Quad channel DDR3 4x QuickPath No Unknown LGA1366 Q4 2009 / H1 2010 - ?
Extreme desktop Triple channel DDR3 2x QuickPath
Performance desktop
Mainstream desktop
Clarkdale Mainstream to value desktop 256 KB L2/core
2-4 (4-8)
Beckton (Nehalem-EX) MP server 45 nm 8 (16) 256 KB L2/core
24 MB shared L3
Quad channel FB-DIMM2 4x QuickPath 130~150 W LGA1567 H2 2009 - ?
Gainestown DP server 4 (8) 256 KB L2/core
8 MB shared L3
Dual and Triple channel DDR3
800/1066/1333/1600 MHz
2x QuickPath LGA1366 Q3 2008 - Q4 2009
Bloomfield Extreme desktop 3.2 GHz $999 1x 6.4 GT/s
QuickPath
Nov 2008 - Q4 2009
Performance desktop 2.93 GHz $562 1x 4.8 GT/s
QuickPath
Nov 2008 - Q3 2009
Mainstream desktop 2.66 GHz $284
Lynnfield Performance desktop 2.xx GHz < $200? Dual channel DDR3
800/1066/1333 MHz
DMI x4/x2
PCI Express 2.0
95 W LGA1160 Q4 2009 - ?
Mainstream desktop
Clarksfield Extreme mobile 45 nm or 32 nm 55 W mPGA 989
Performance mobile 45 W
Havendale Mainstream desktop 45 nm 2 (4) 3 GHz $90-$279 256 KB L2/core
4 MB shared L3
Yes 93 W LGA1160 H2 2009 - ?
75 W
Value desktop 93 W
75 W
Auburndale
(Gilo CPU+
Ironlake GPU)
Performance mobile 45 nm or 32 nm < $100? 45 W mPGA 989 January 2010 - ?
Mainstream mobile
Power optimized mobile 35 W

Note: "Extreme" processors have an unlocked clock multiplier. TDP values for CPUs with integrated GPUs include the GPU. Prices are for batches of 1000.

Successor

Westmere (formerly Nehalem-C) is the name given to the 32 nm shrink of Nehalem. Westmere should be ready for a 2009 release provided that Intel stays on target with its roadmap. However, it appears that the bulk of Westmere's versions, excluding mobile versions, will be released sometime in 2010. From various sources, Westmere's changes and improvements from Nehalem have been reported as follows:

  • 32 nm process.
  • Native six-core processors.
    • The successor to Bloomfield and Gainestown is either quad-core or six-core.
  • A new set of instructions that gives over 3x the encryption and decryption rate of AES processes compared to before.
    • Delivers six new instructions that will be used by the Advanced Encryption Standard (AES) algorithm and also an instruction that will perform carry-less multiplication (PCLMULQDQ). Those instructions allow the processor to perform hardware accelerated encryption not only providing a faster execution but also protects against software targeted attacks.
    • AES-NI may be included in the integrated graphics of Westmere.
  • Westmere's integrated graphics may be released at the same time as the processor.
  • Improved virtualization latency.
  • Release dates:
    • Q4 2009 to January 2010 for mobile chips.
    • Late 2009 or early 2010 for DP server chips.
    • H1 2010 for high-end desktop chips (Bloomfield successor).
    • H2 2010 for mainstream and value desktop chips, assuming Westmere is released for that segment.

The successor to Westmere will be Sandy Bridge, scheduled for release in 2010, according to Intel roadmaps.

Then, the successor to Sandy Bridge will be Haswell, scheduled for release in 2012. It will come with a new cache subsystem, a FMA (fused multiply-add) unit, and a vectorial coprocessor

See also

References

Further reading

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