Arm Joins CXL Making the Path Forward Clear

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Compute Express Link CXL Announcement Cover
Compute Express Link CXL Announcement Cover

In a quick post today, Arm announced that it is joining the Compute Express Link (CXL) Consortium. Indeed, it actually went a bit further. With Arm joining Intel and AMD also becoming a member, the path forward is clear: we are moving to a CXL future in the upcoming PCIe Gen5 era.

Why Arm Joining CXL Is Important

Arm has been one of, if not the, biggest supporter of CCIX. We are already seeing designs like the Huawei Kunpeng 920 64-Core Arm server CPU with CCIX and PCIe Gen4 launched. Further, accelerator companies like Xilinx have been active in promoting CCIX in their shipping FPGAs. An example is the recently announced Xilinx Alveo U50 FPGA card for data center acceleration.

By joining the CXL Consortium, Arm is signaling to its partners, and the server ecosystem as a whole, that CXL is its path forward. From Arm’s announcement:

Arm brings to the table its track record in establishing a full software framework and aims to promote the migration to CXL as the interface to the accelerators and memory expansion. We expect to maintain CCIX to support inter-package chip-to-chip interface that is currently not in the scope of CXL. We will continue to support customer solutions based on existing CCIX hardware. (Source: Arm)

CCIX is not dead for the time being, it is now just limited in scope. Accelerator companies and even memory controller companies (e.g. Microchip SMC 1000 For The Serial Attached Memory Future) now know CCIX will have a limited role in the Arm ecosystem, likely no role in the Intel ecosystem, and potentially now no go-forward role with AMD.

Stephen Van Doren CXL Interconnect PCIe Gen5 And Gen6
Stephen Van Doren CXL Interconnect PCIe Gen5 And Gen6

With Arm, Intel, and AMD all signaling support for CXL, the war is essentially over before the first device has shipped. That is actually great news. The server industry figured this out across vendors before the PCIe Gen5 hardware was even shipped. That avoids the old “VHS won but I have a Betamax” conundrum.

Arm also re-affirmed support for Gen-Z in its announcement. STH covered how Dell EMC (and HPE) see CXL and Gen-Z co-existing in Gen-Z in Dell EMC PowerEdge MX and CXL Implications. If you want to learn more about CXL, see our New CXL Details at Intel Interconnect Day 2019 piece. Everyone has been sniffing around CXL, but with Arm today favoring CXL over CCIX that will have a big market impact.

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