Just before Flash Memory Summit 2018, we have an announcement of Microsemi PCIe Gen4 switches. Microchip just bought Microsemi. During this transition period, and including the latest RAID controllers, Microchip Microsemi Adaptec SmartRAID 3162-8i RAID adapters the company is keeping the Microsemi branding. PCIe Gen4 is about to get thrust into the spotlight as IBM POWER9 already supports the new standard and AMD EPYC “Rome” platforms are expected to support PCIe Gen4 as well. These new switches are important because they give the industry an alternative to Broadcom PLX chips. For the flash space, we covered the business side of PLX acquisition: Impediment to NVMe everywhere.
Microchip Microsemi PCIe Gen4 Switches
PCIe Gen4 or PCIe 4.0 is a big deal in the industry. Starting with PCIe 4.0 peripherals will get twice the bandwidth as previous generations, and see lower latencies. Here is a chart of the different PCIe versions and how speed has increased:
| Generation | Per Lane Bandwidth | x16 Slot Bandwidth |
|---|---|---|
| PCI Express 1.0 |
2 GT/s | 32 GT/s |
| PCI Express 2.0 |
4 GT/s | 64 GT/s |
| PCI Express 3.0 |
8 GT/s | 126 GT/s |
| PCI Express 4.0 |
16 GT/s | 252 GT/s |
As it is released, PCIe 4.0 will improve host to PCIe performance considerably. In the context of Microchip’s Microsemi Switchtec PCIe switches, that means more switch to host bandwidth. It also means that for GPUs and FPGAs that need fast PCIe device to PCIe device communication, the new standard will help considerably. You can see an example of the need for PCIe bandwidth in single root deep learning servers. (See: Single Root v Dual Root for Deep Learning GPU to GPU Systems.)
On the networking side, servers are severely constrained with PCIe Gen3. PCIe Gen3 can support 50GbE and Mellanox’s 56GbE, and FDR Infiniband in a x8 slot. Those x8 slots are the mainstays of the server world. To get EDR Infiniband, Omni-Path 100 (in PCIe form), or 100GbE, one needs a PCIe 3.0 x16 slot to provide bandwidth for a single port. PCIe 4.0 will provide single-port PCIe bandwidth in a common x8 form factor. It will also support dual-port 100GbE or single port 200GbE in a single PCIe 4.0 x16 slot.
Final Words
The Microchip Microsemi Switchtec solutions are important on a variety of levels. First, the ecosystem ramp from PCIe 3.0 to PCIe 4.0 is sorely needed. This furthers that goal. Second, it provides an alternative to the Broadcom/ PLX regime which post-acquisition was a nightmare for hardware providers in the space.
