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Rumors suggest AMD’s Zen servers will pack 32 cores, serious heat

We know that AMD is planning to ramp its Zen family from small form factor systems into large, big-iron servers, but exact product details remain scarce on the ground. A new report claims to put some hard figures behind the estimates, and while all such claims should be taken with a mountain of salt, the basic argument is plausible.

According to Fudzilla, AMD’s top-end chip (codenamed Naples) will ship in a 32-core / 64-thread configuration with 64MB of total L3 cache, eight memory controllers, and 128 PCI Express lanes. The CPU will supposedly ship in TDPs from 35W to 180W with support for up to 16x 10GbE ethernet controllers, alongside support for up to 32 SATA drives.

While all of this is rumor, some of it is at least in line with overall trends in the microprocessor industry, as well as rumors we heard earlier this year courtesy of a CERN presentation. Intel offers a 24-core / 48-thread version of its top-end Xeon hardware, so it’s not hard to believe that AMD might try to one-up Intel with an additional eight cores of CPU. AMD is thought to be using a Multi-Chip Module (MCM) configuration, which would also make sense — it can connect two 16-core chips on the same physical silicon using a high-bandwidth interconnect.

The 180W maximum TDP also makes sense, given that Intel’s 24-core Broadwell Xeons have a maximum rated TDP of 165W. (Remember, these chips are destined for server rooms, where pesky issues like human hearing aren’t so much of a consideration). Eight memory controllers seems quite high, but again, it’s possible that AMD wants to brute-force an advantage over Intel. 128 PCI Express lanes is extremely high, but this could make sense if a significant number of those lanes are dedicated to the MCM itself. Imagine a scenario where 32 PCI Express 3.0 lanes are dedicated to intra-package communication, 32 are reserved for peripherals, and the remaining 64 are dedicated to communicating with other CPUs in 2-way or 4-way systems.

Rumors aren’t automatically true just because they make sense, and it’s common for companies to propose and even prototype solutions that don’t come to market for a variety of reasons. Until we know more about Zen’s clock speeds and per-thread IPC, it’s impossible to predict how well the core will compete against Intel’s top-end server solutions. Zen isn’t expected to debut in servers until after its desktop launch (currently expected late this year or early next); the company will spend a significant chunk of the next 6-8 months determining exactly which core counts and TDP envelopes will help it regain lost market share and challenge Intel most effectively. When Opteron was running rings around Xeon 10-12 years ago, it was particularly strong in the multi-socket market. AMD may be banking on pulling off that particular trick twice.

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