Mt. Everest – Tallest on Earth

Mt. Everest is the tallest mountain here on Earth, the pinnacle of climbing challenges.  There is no going higher then Mt. Everest.  At Intel the pseudo-unofficial codename for the absolute fastest speed bin of a particular processor is…Everest.  Everest processors are the fastest an architecture will so reliably.  Sometimes these processors end up an normal products, available for consumers to purchase.  The first good example of this is the Core 2 Extreme QX9775 Yorkfield core (Core Architecture).  They were a quad-core processor running at 3.2GHz, fast but not mind blazingly so.  The Xeon equivalent was the X5492 (Harpertown) 4-core at 3.4GHz.

Xeon X5698 – Westmere – 4.4GHz – Mid 2010

The next well know Everest was a chip based on the Westmere (shrink of Nehalem) architecture.  The Westmere Everest became known as the Xeon X5698, and was available for OEMs only, in fact it was a special order processor made with one particular type of client in mind. These were to be used for High Frequency Stock traders, and other such high speed transactional processing, where the ability to complete trades as fast, and reliability as possible is the entire nature of the business.  This means that single thread performance is far more important then having multiple core, and as such, the X5698 uses a 6-core die with only 2 cores active, but retaining access to the entire 12MB of L3 cache.  Clock speed was fixed at 4.4GHz, the cores did not reduce frequency as processing demands changed, as this would introduce uncertainty in how fast it would complete a given task. Doing task ‘X’ should take a predictable amount of time and not depend on what speed the processor chose to run at.  The next fastest Westmere processor was the X5690, which was a 6-core (all cores enabled) running at 3.46GHz (the same chip essentially as the Core i7 990X).  The X5698 was nearly 1GHz faster.  The X5690 cost around $1800, where as the X5698 cost around $20,000 EACH (based on costs OEMs charged to add a 2nd one so they may have marked it up some).  The impressive thing is that these chips would go faster.  Intel sampled 4.66GHz versions and Supermicro built systems using X5698’s overclocked to 4.8GHz.  All this back in 2011.

4.4GHz Jaketown (Sandy Bridge) Everest Sample 2010-2011

Intel’s next architecture was known as Sandy Bridge.  Sandy Bridge topped at at 3.5GHz (6-cores) for the Core i7 Extreme 3970X and 3.6GHz for the 4-core i7-3820 and similar Xeon E5-1620.  Intel demo’d an air cooled Sandy Bridge running on stage for a presentation at 4.9GHz, so the core certainly had some room to spare.  There is no documentation (that I could find) that Intel actually released anything faster then 3.6GHz, at least that I could find, but evidence suggests that they at least were thinking about it.  The picture is a Sandy Bridge Xeon in LGA2011 marked JKT EVEREST SS 4.4GHZ INTERNAL USE ONLY. JKT is short for Jaketown, Intel’s codename for the 32nm Xeon E5-2600 series.  That gives a very good idea what this processor was to be.  SS is likely to be a Single Socket (as often at those speeds getting dual systems working can be tricky).  Sandy was certainly capable of hitting 4.4GHz, with 4-core, and even air cooling, so perhaps these were samples for a limited OEM run, much like the previous Westmere X5698 processors.

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Intel Sandy Bridge-EP 8-core dies with 6 cores enabled. Note the TOP and BOTTOM markings (click image for large version)

Recently a pair of interesting Intel Engineering Samples came to The CPU Shack.  They are in a LGA2011 package and dated week 33 of 2010.  The part number is CM8062103008562 which makes them some rather early Sandy Bridge-EP samples.  The original Sandy Bridge was demo’d in 2009 and released in early 2011.  So Intel was making the next version, even before the original made it to market.  The ‘EP’ was finally released in late 2011, over a year after these samples were made.  Sandy Bridge-EP brought some enhancements to the architecture, including support for 8-core processors (doubling the original 4).  The layout was also rather different, with the cores and peripherals laid out such that a bi-direction communications ring could handle all inter-chip communication.

Sandy Bridge-EP 8-core die layout. Note the ring around the inside that provides communications between the peripherals on the top and bottom, and the 8-cores. (image originally from pc.watch.impress.co.jp)

Sandy Bridge EP supports 2, 4, 6 and 8 cores but Intel only produced two die versions, one with 4 cores, and one with 8 cores.  A die with 4 cores could be made to work as a dual core or quad, and an 8-core die could conceivably be used to handle any of the core counts.  This greatly simplifies manufacturing.  The less physical versions of a wafer you are making, the better optimized the process can be made.  If a bug or errata is found only 2 mask-sets need updated, rather then one for every core count/cache combination.  This however presents an interesting question..What happens when you disable cores?

That is the purpose of the above samples, testing the effects of disabling a pair of cores on an 8-core die.  Both of the samples are a 6-core processor, but with 2 different cores disabled in each.  One has the ‘TOP’ six cores active, and the other the ‘BOTTOM’ six cores are active.  This may seem redundant but here the physical position of the cores really matters.  With 2 cores disabled this changes the timing in the ring bus around the die, and this may effect performance, so had to be tested.  Timing may have been changed slightly to account for the differences, and it may have been found that disabling 2 on the bottom resulted in different timings then disabling the 2 on the top.

Ideally Intel wants to have the ability to disable ANY combination of cores/cache on the die.  If a core or cache segment is defective, it should not result in the entire die being wasted, so a lot of testing was done to determine how to make the design as adaptable as possible.  Its rare we get to see a part from this testng, but we all get to enjoy its results.