Zen architecture pioneer Jim Keller feels AMD was stupid to cancel the K12 Core ARM processor

Jim Keller is a familiar name to those who follow the semi-conductor industry, and he has been the brains behind several important CPU generations from the VAX 8800 to Apple's A4 and A5 SoCs and AMD's Zen architectures. At AMD, Keller was also responsible for designing the K12 Core, which is an ARM-based processor that AMD had to cancel after his departure from the company.

In an interaction with the Department of Computer Science and Automation at the Indian Institute of Science (IISc), Bengaluru, Keller opined that AMD "stupidly canceled" the K12. 

The AMD K12 Core was first announced back in 2016 and was based on a 64-bit ARMv8 design. AMD shelved the project before its slated 2017 release, but we've been hearing rumors that the company isn't done with ARM just yet. A roadmap leaked in 2020 indicating a possible revival of the K12 architecture. By then Intel had already launched Lakefield hybrid x86 designs and Apple was on the verge of going full ARM. 

Apple eventually announced the M1 SoC, and soon rumors of AMD having an M1 competitor in the works started cropping up. AMD had published several patents by then dealing with "Instruction subset implementation for low power operation". However, we haven't heard much after this.

According to Jim, he had designed CPU plans up to the Zen 3 generation, which means Zen 4 and later were designed by a new team at AMD. Jim's plan with the K12 was to work on a new decode unit since the cache and execution unit design for ARM and x86 were almost similar, but AMD had other plans after he left. This included diversifying Zen across desktop, HEDT, laptop, server, embedded, and semi-custom platforms such as the Xbox Series X/S and the PlayStation 5. 

Jim described his tenure at AMD as "fun" and, unlike management, said he wasn't scared of making changes as he himself was the architect.

Though AMD's ARM plans aren't exactly clear at the moment, we might eventually see an AMD-branded ARM CPU soon. AMD CFO Devinder Kumar confirmed last year that the company isn't shying on developing ARM chips and that it has seen many requests from customers for ARM-based solutions.

It remains to be seen which market segment would AMD address first once its ARM plans bear fruition.

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