Building on their recent announcement of PCIe 5.0 retimers, Microchip has announced their first PCIe 5.0 switches, as part of their Switchtec PFX product line. On paper these look like a very straightforward update to their existing Switchtec PFX switches for PCIe 4.0, carrying over all the important features but doubling the speed.
The final version of the PCI Express 5.0 specification was released in May 2019, but significant adoption is not expected to begin until Intel’s Sapphire Rapids Xeon processors ship, planned for later this year. Microchip is positioning themselves to be one of the most important vendors helping enable the transition, and they expect to be the only company offering both switches and retimers for PCIe 5.0. Components like switches and retimers are becoming increasingly important with each iteration of PCIe as higher speeds are achieved at the cost of range; servers using PCIe 5.0 will only be able to put a handful of devices close enough to the CPU to operate at PCIe 5.0 speeds without some kind of repeater. Retimers like Microchip’s XpressConnect parts are simple pass-through repeaters, while switches like the new Switchtec PFX parts can fan out PCIe connectivity from one or more uplink ports to numerous downstream ports.
As with the PCIe 4.0 members of the Switchtec PFX product line, the new PCIe 5.0 switches will be available with lane counts from 28 to 100. These switches support port bifurcation down to x2 links, with bifurcation down to x1 supported by some of the lanes on the switch. The switches also support up to 48 Non-Transparent Bridges (NTBs), allowing for large multi-host PCIe fabrics to be assembled using several switches. However, initial demand for PCIe is expected to center around GPUs, machine learning accelerators and high-speed NICs, so many of those advanced features will be underutilized early on, and the chips will be primarily used to feed those extremely bandwidth-hungry peripherals with an x16 link each. SSDs using just two or four lanes each are expected to be slower about moving to PCIe 5.0.
The new PCIe 5.0 Switchtec PFX switches are currently sampling to select customers, including a development/evaluation board based around the 100-lane switch. Microchip wouldn’t disclose any pricing information for the new switches, but they are bound to be more expensive than the PCIe gen4 switches with the same lane counts. Power consumption is also going up, but Microchip wouldn’t quantify the change.
Microchip’s lineup of PCIe switches for earlier generations also includes the Switchtec PSX and PAX families with more advanced functionality than the PFX switches. PCIe 5.0 versions of the PSX and PAX families have not been announced, but it’s normal for those versions to come later. Microchip’s only competition for leading-edge PCIe switches comes from Broadcom/PLX PEX switches. Broadcom has not yet publicly announced their PCIe 5.0 switches, but they are doubtless also planning to take advantage of the launch of Intel’s Sapphire Rapids platform.