CXL May Have Just Won as AMD Joins CXL

There are few points more universally taken as a given as I talk to server vendors other than we are about to see a new generation of interconnects. Some of the more well-known are Gen-Z and CCIX. This year, Intel announced Compute Express Link or CXL as a new open standard. Since then, the Compute Express Link consortium has seen a rapid increase in membership. Today, AMD announced that it has joined the consortium. While that is still short of saying that AMD supports CXL in its products or will do so in the PCIe Gen5 products, it does lend a lot of credence to the notion that the industry is headed that way.

AMD Joins CXL

If you saw my June 2019 Notes from Talking Servers with Forrest Norrod SVP and GM at AMD you may have seen this passage:

S3. Does AMD have any plans to support Compute Express Link also known as CXL?

I asked this, fully expecting to get a “no.” Instead, Forrest was more diplomatic and thoughtful in his response.

• AMD has not announced CXL support yet.
• AMD will monitor CXL. If it is open, and truly open, is something that AMD will look at.
• If there is a push in the silicon industry for CXL, AMD will consider adopting it.
• Forrest was careful not to say that AMD will never support CXL. He just said that AMD wanted to ensure that it would be adopted in the market and is a truly open standard.

(Source: STH June 13, 2019)

My sense is that this is something that Forrest knew was at least a possibility a month ago. I would also venture to guess that the conditions listed above were more than abstract ideas governing whether AMD would join CXL.

What Does the Future Look Like

The big “so what” with AMD joining CXL, if one assumes that PCIe Gen5 AMD products will support the standard, is adoption. With OpenCAPI, CCIX, Gen-Z already out there, and then Intel releasing CXL, there were four standards that could compete at different parts of the stack. You can read more about the Compute Express Link Cache Coherent Interconnect from our Interconnect Day 2019 coverage.

Asking HPE and Dell about how Gen-Z and CXL will play together was enlightening. We published our Gen-Z in Dell EMC PowerEdge MX and CXL Implications piece where you can read more details. From both the Dell and HPE perspectives, and they are the top two server vendors, Gen-Z and CXL can co-exist. CXL will live inside the domain of a node. Gen-Z will help bridge from chassis to chassis.

What remains to be seen is if work can be done to homogenize everything into a single set of standards. If we see a Gen-Z plus CXL amalgamation, that will likely become the winner without having to rely upon two standards bodies.