Microarchitecture refers to how an instruction set architecture is implemented in a processor. It focuses on aspects like chip area, power consumption, and complexity. Nehalem was Intel's latest microarchitecture at the time, featuring an integrated memory controller, QuickPath interconnect, and improvements in performance and power efficiency over previous architectures. Its successors included Westmere, Sandy Bridge, and Haswell.

2. What is Micro architecture?
Microarchitecture (µarch or  Chip area/cost
uarch), is the way a given ISA is
implemented on a processor.  Power consumption
 Logic complexity
Micro architecture design focus  Ease of connectivity
on these aspects
 Manufacturability
 Ease of debugging
 Testability

3. Nehalem ?
 Is the codename for It was then followed by several
thelatest Intel processor Xeon processors and by i3 and i5.
micro architecture.
Was supposed to be latest evolution
 The first processor of NetBurst, but was renamed as
‘Nehalem’
released with the
Nehalem architecture HT is reintroduced along with an L3
was the desktop Core i7 cache to achieve higher clock
speeds and energy efficiency.
(Nov 2008).

4. Technology
 Wide range of two, four, six,  Integrated memory
eight, ten or twelve core controller supporting two or
processors. three memory channels
 Initial release with 45nm of DDR3 SDRAM or four FB-
manufacturing process, followed DIMM2 channel.
by 32nm variants.It allows more  Integrated graphics processor
number of transistors in a single (IGP) located off-die, but in the
die (731 million in quad core same CPU package.
variant!).

5. Technology (..contd)
 A new point-to-point processor  Simultaneous multithreading
interconnect, the Intel QuickPath (Hyper Threading) by multiple
Interconnect, in high-end cores which enables two threads
models, replacing the per core.
legacy front side bus
 Integration of PCI  Native (monolithic) quad- and
Express and Direct Media octal-core processor.
Interface into the processor in  33% more in-flight micro-
mid-range models, replacing operations than Core 2 uarch.
the northbridge

6. Technology (..contd)
 The following caches:
 32 KB L1 instruction and 32 KB L1 data cache per core
 256 KB L2 cache per core
 4–12 MB L3 cache (2MB/Core) shared by all cores
 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.

7. Performance and Power Optimizations
 1.1× to 1.25× the single-threaded performance or 1.2× to 2×
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 a 10% increase in power
usage.
 Per Core, clock-for-clock, Nehalem provides a 15–20% increase
in performance compared to Penryn

8. Processor Release Timeline
The successor to Nehalem and Westmere will be Sandy Bridge, scheduled for release in late
2010, according to statements by Intel. 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 vector coprocessor.

9. Related Definitions (1/4)
 An instruction set, or instruction set
architecture (ISA), is the part of the computer
architecture related to programming, including the
native data types, instructions, registers, addressing
modes, memory architecture, interrupt and exception
handling, and external I/O. ISA includes specifications
of the set of opcodes (machine language), and the
native commands implemented by a particular
processor

10. Related Definitions (2/4)
 Per the International Technology Roadmap for
Semiconductors, the 45 nm technology node should
refer to the average half-pitch of a memory cell
manufactured at around the 2007–2008 time frame.
 QuickPath is a core to core interconnection that
eases inter processor data transfer with a bandwidth
of 25.6GB/Second.

11. Related Definitions (3/4)
Front side Bus is the the bus that
carries data between the CPU and
the northbridge.
Back side bus is the bus between
CPU and cache memory.

12. Related Definitions (4/4)
 branch predictor is a digital circuit that tries to guess
which way a branch (e.g. an if-then-else structure) will
go before this is known for sure.