Die shots of Intel's test shuttle 45nm SRAM lithography for "Penryn"

Intel's long-term microarchitecture roadmap

An early tri-gate design from Intel
What's the absolute bleeding edge in Intel CPU design for the next five years? "Penryn," "Nehalem" and "Gesher"

No one would doubt that Intel's Core 2 Duo is perhaps one of the most hyped and anticipated processor launches since the K8.  The processor, expected to start shipping on July 23, 2006, is Intel's first major transition in desktop microarchitecture since the Willamette core was introduced in 2000. 

Conroe and its derivatives are a step away from Intel's former flagship NetBurst, but even these processors are a bit of a dying breed: during Intel's shift to 45nm, the company will no longer focus on derived microprocessor cores in favor of refined unified core architectures.  For example, later this year Intel is expected to release Allendale, a dual core Conroe-based processor with only 2MB of L2 cache.  From what Intel has stated from forward looking statements and roadmaps, this sort of practice will stop. 

One possibility as to how this will work will be in the way Intel packages its processors.  For example Intel's Presler is essentially a Cedar Mill processor with two dice coupled on the same package.  Likewise, Intel's Kentsfield processor is two Conroe dice coupled on a single package to make a quad-core processor.  Even though your server and desktop processor will have the same processor core on Intel's future architectures, the logical way to differentiate the role of these CPUs will be the number of dice per package.

Intel announced the majority of its long-term architecture plans in April of this year. During this same announcement, Intel detailed that the Core microarchitecture would survive into 2008 with the 45nm Penryn core. 

Penryn, which will be based on Intel's lithography process known as P1266, is a 45nm unified core set for launch in 2007 that is also expected to stay into production into 2008.  Intel has already produced SRAM samples for 45nm CPUs, as demonstrated in the lithography shot on the right.  Aside from the process shrink on Penryn, the major divergence in design from Conroe is the new material design.  With P1266, Intel shifts away from Silicon Dioxide gate dielectrics -- a process the company has used since the mid-90s -- to High-k dielectrics.  With new dielectric techniques, the company will also revamp its gate electrodes to metal instead of Polysilicon derivatives.  The last major materials change of such magnitude occurred when Intel moved from Silicon to Strained Silicon in 2002, which is still slated for use in P1266 and beyond.

According to Intel's long term roadmap, Penryn will become the last "Core" (NGMA) microarchitecture, but it will not become the last 45nm generation.  A new architecture, based on the Nehalem core, will make an appearance in 2008.  This Core successor, dubbed by many as NGMA2, will essentially take all of the 45nm manufacturing principles of Penryn and apply them to the totally new Nehalem architecture.  This transition will be very similar to the P6+ transition with Yonah from Dothan to Conroe

If P1266 was radically different from the 65nm Core CPU process, P1268 takes what is normal on 45nm and throws it out the window.  The first P1268 processor will use a CPU codename that Intel has publically announced as Nehalem-CNehalem-C is still based on the Nehalem (NGMA2) microarchitecture, but is a die shrink from 45nm to 32nm. P1268 employs all of the neat manufacturing techniques found on P1266, but may use a totally different lithography process called EUV, or Extreme Ultraviolet. Although it sounds trivial to swap a traditional DUV lithography setup with an EUV one, there is a fundamental problem with EUV that prevents foundries from doing so; the EUV wavelength is so small at 13.4nm that virtually every material absorbs the wave including the lenses and atoms in the air. EUV must be done in a vacuum with reflective surfaces instead of lenses to focus and redirect the lithography. 

However, EUV isn't the only radically new tool in Intel's arsenal for 2009.  According to Intel's forward statements, Nehalem-C is succeeded by Gesher, the third in Intel's next generation microarchitecture designs uniquely dubbed NGMA3.  Intel hinted last week during the 2006 VLSI symposium that it will start using tri-gate transistors on its 32 or 22nm production processors.  Since the 1950s, transistors have been strictly planar designs, with gates that lay flat across the substrate.  A tri-gate design is unique in the fact that a single gate is stacked on top of two vertical gates allowing for essentially three times the surface area for electrons to travel.  Whether or not these tri-gates will appear on Gesher or its 22nm derivative have not been announced.

Even beyond Gesher and its 22nm derivative, Intel has a lot of technologies in its roadmap.  One technology proposed to replace tri-gates is by using silicon nanowires surrounded by a metal gate to increase surface area even more. Intel laboratories have also experimented with carbon nanotubes a mere 1.4nm in diameter as a future transistor material, yet these materials won't show up until 2013 at the earliest. 

If anything, here are the big points to keep in mind for Life After Conroe:

  • Intel will unify its processor architectures -- no more Merom/Conroe/Woodcrest derivatives.  The processor core that you use in your server will essentially be the same chip you use in your notebook.
  • Parallel design -- The Nehalem team is already working on its 45nm processor.  Penryn is a "meet you in the middle" project between Core and Nehalem, which is also undergoing development.  The same leapfrogging will occur with Nehalem and Gesher.
  • P1266 lithography (Penryn family processors) will use radically different manufacturing techniques -- High-k dielectrics, metal gate electrodes
  • P1268 (Gesher and Nehalem-C) switches from 193nm DUV lithography to EUV 13.4nm lithography.

"We basically took a look at this situation and said, this is bullshit." -- Newegg Chief Legal Officer Lee Cheng's take on patent troll Soverain
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