[The Exiled]

Will AMD get back into ARM server chips?

There was a bit of a kerfuffle this week when it looked like AMD was changing its position a little bit on whether or not it would get back into designing and selling server chips based on the Arm architecture. The funny thing is that the world has changed around AMD, and a lot of it for the good, as its EPYC X86 server processors have attained around ten percent market share (by shipments), but its position on Arm servers has not really changed. AMD’s top brass has said all along that if customers wanted Arm chips, it would make them. Well, maybe AMD’s position, internally, has changed just a little now that the server market has changed so much since the summer of 2015 when AMD stopped its “SkyBridge” X86-Arm shared socket effort, launched in 2014 with much fanfare. Prior to that announcement, AMD’s Opteron Arm server chips based on its homegrown “K12” core were expected in 2016 and were pushed out to 2017, and they were SoCs that combined Arm cores and GPUs, much as the “Seattle” Opteron A110 was. Seattle fizzled because it was too underpowered to do anything useful in the datacenter. So AMD started shutting things down, killing off SeaMicro microservers and its interconnect, killing off Arm server chips, so it could just hunker down on the EPYC server CPU. Because, frankly, the Arm server chip demand never materialized.

AMD has plenty of interesting options when it comes to Arm server chips. First of all, as Cavium, which is now part of Marvell, proved so well and as AMD proved with its Seattle Arm chips, it is not all that hard to do a global replace and put Arm cores in the same place where an Octeon NPU core or an X86 CPU core is in a processor design. The uncore stuff can be recycled, and if you are an Arm licensee as AMD is, you can take some of the stuff in the guts of the core — branch predictors, caches and cache hierarchies, vector units, other accelerators, memory controllers, and peripheral controllers and reuse these elements in an Arm server chip. So if a hyperscaler (not likely a public cloud since no one has a lot of Arm server workloads outside of the hyperscalers) doesn’t want to do an Arm server chip design all by its lonesome, they could hire AMD to do it.

While that would be interesting, what we think would actually be far more interesting is for AMD to pull a sequel to the SkyBridge effort and create a common socket for X86 and Arm server chips that is completely neutral about what kind of chip is plugged in. This is a real value for those who want flexibility, and if it really wanted to hedge its bets, it could do server CPU designs that had a lot of the components between X86 and Arm — and maybe someday RISC-V — be as common as possible.

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