Today, Broadcom is firing a big shot at Astera Labs and a few others with its new PCIe and CXL Retimer family. If you have been following STH, you will know that PCIe retimers have become critically important in PCIe Gen5 servers, especially those that cover large physical footprints like AI and storage servers. A PCIe retimer, in simplest terms, is a chip that sits in a PCIe (or CXL that is built upon PCIe) path and boosts the signal so it can span longer distances. As a result, if you look at a modern AI server, there are usually several retimers each costing upwards of $20 to span the distance between various high-speed components. Broadcom saw competition in the market and had previously decided to let others take it. Now, it is back in the market with PCIe Gen5 and Gen6 retimers with CXL support.
Broadcom Vantage 5 and Vantage 6 PCIe and CXL Retimers
Since everything is AI these days, Broadcom showed us a slide discussing the PCIe retimer use in AI servers. This is more than just hype, as retimers are often used in GPU servers because there are many devices, and the reach of PCIe signaling is much further than in traditional 1U/ 2U servers. On one hand, this is a slide using the AI trend over something like storage. On the other hand, it is absolutely spot-on as an application.
Broadcom’s new PCIe controllers, dubbed the Vantage 5 and Vantage 6 for the PCIe Gen5 and PCIe Gen6 eras, have 16 and 8 lane options. Those lanes can be bifurcated so if you had four PCIe Gen5 x4 drives they can share a 16-lane retimer. Broadcom is also supporting CXL an low latencies. Its SerDes expertise comes from some of the learnings from the higher-speed SerDes on the networking side of the company.
Broadcom is building Vantage 5 and Vantage 6 on 5nm. That means Broadcom’s controllers will use a few watts less per chip than its competition. You may see this slide and think that even 6W does not sound like a lot, but then look at the AI server diagram above and think of it like every ~166 AI servers using Broadcom Vantage 5 will save enough power to fit one more 8x GPU server into a data center power budget. Also, in liquid-cooled servers with cold plates oftentimes only the CPUs and GPUs/ AI accelerators are liquid cooled with other components being cooled using fans. See our Gigabyte-CoolIT building from the ground up, Supermicro NVIDIA AI liquid cooling, and QCT liquid cooling as examples.
Broadcom has entire kits from test boards, retimers, PCIe switches and so forth so that their retimers and really PCIe/ CXL ecosystem products can be implemented quickly. That also means Broadcom has its software suite for switches and retimers to help diagnose corner cases and issues.
Broadcom is also committing to staying in the retimer business with a roadmap that goes from the PCIe Gen5/ CXL 2.0 Vantage 5 and Atlas 2 today to the PCIe Gen6/ CXL 3.1 Vantage 6 and Atlas 3 later this year for 2025 systems. There is a roadmap Vantage 7 and Atlas 4 as the retimer and switch solutions for PCIe Gen7.
Something important here is that Broadcom is providing both switches and retimers and our sense is that it will be able to bundle those. Today, it is not uncommon to see a Broadcom PCIe switch with an Astera Labs retimer, but there is a lot of power in being able to sell the PCIe fabric together for larger systems with a common set of debug tools.
Final Words
Astera Labs has come out of almost nowhere and is now seeking a multi-billion dollar valuation in its IPO. To say that Astera Labs has been selling its retimers like crazy in the void when Broadcom did not have a Gen5 controller would be an understatement. It looks like Broadcom has noticed and has a customer base ready to use its retimer solutions. Timing-wise, Broadcom was late to the PCIe Gen5 cycle, but it also seems committed to being in the market for the launches of PCIe Gen6 and PCIe Gen7 cycle in servers.
Update: Since I got a lot of requests for consulting calls on the PCIe retimer market after our previous piece, we have an Axautik Group LLC Research Short for the Astera Labs and Broadcom releases over the past week to answer some of the common questions I have fielded recently.
