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.

Source: Microchip

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  • Deicidium369 - Wednesday, February 3, 2021 - link

    PCIe5 on Servers makes perfect sense - but on Workstation Class (we use Xeon Scalable for our Engineering CAD/CAE workstations)there is no advantage for PCIe5 over PCIe4 - I can get NIC at 200GBE/IB EDR that are PCIe4 x16... so until 800GBE faster drops (My Cisco 93600 switches support 400Gb/s on some ports - yet you can't even find a 400GBE NIC) PCIe4 will suffice.

    I cannot see the use case for PCIe5 slots on a desktop PC - even PCIe4 is overkill in most cases.

    Sounds like you have been in the industry for a while - remember the near MIL-Spec motherboards that Compaq used to make? PCIe5 on the desktop (presenting as PCIe5 slots) would need to be that level or better.
  • back2future - Thursday, February 4, 2021 - link

    Saturating trans ocean fibre bundles networking capacity needs one 16lanes PCIe6 (then), 4320p (120Hz) can be provided on 2lanes PCIe4 or 1lane >PCIe5 and Thunderbolt (40Gb/s) on 4lanes PCIe4 or 2lanes >PCIe5. With arriving technological changes towards PCIe6 (>=2021) that's probably one of most interesting parts on cpu&PCIe carrier boards these days (Considering laser/fibre transmission limits <>40Tb/s and <1Tb/s, combined memory&storage development > 1lane PCIe5, You mentioned on comment before, or maybe also power supply on 24/7 devices and temperature management). These parts spreading into consumer level provides chances for new development concepts (including user side, interest related data filtering supported through ai)?
    What's beyond light for data transmission ...
  • Tomatotech - Thursday, February 4, 2021 - link

    "I cannot see the use case for PCIe5 slots on a desktop PC - even PCIe4 is overkill in most cases."

    NVME drives are already bumping near the top of PCIe4 right now. Moving forward will require PCIe5. At least for marketing numbers - I'm aware there are many other parts to NVME performance that could be improved.
  • mode_13h - Friday, February 5, 2021 - link

    Not "bumping", as that would imply maxing PCIe 4.0, which they cannot do.

    NAND is about being cheaper and denser, rather than faster. To reach higher speeds, it either comes at the expense of density or by adding channels, each of which is expensive. Even the mighty Samsung cannot resist the urge to go denser, as we see in the case of their slightly disappointing 980 Pro.

    The case that SSDs would make for PCIe 5.0 would be to drop down to x2 lanes (without sacrificing performance). But it sounds like it's not going to be a net savings either for them or the motherboard, so they probably won't.
  • calc76 - Wednesday, February 3, 2021 - link

    There are $80 AMD B550 and $130 AMD X570 boards with PCIe 4.0 slots.

    The reason prices are so high right now is primarily due to very high demand combined with supply chain issues.
  • Alexvrb - Sunday, February 7, 2021 - link

    Dan, the price increases aren't that high because of PCIe 4.0. Look at B550 board launch prices. They weren't THAT much more comparing apples to apples to same-class B450 boards, even without considering the rising component costs. I paid $150 for mine, and there were cheaper options at the time. An equivalent full ATX B450 with a similar VRM config and featureset (minus 4.0) wasn't dramatically less.

    The SUBSEQUENT price increases aren't due to PCIe 4.0, but rather market conditions (look at CPU and GPU prices). Demand is stupid high among both gamers and miners (ughh). I got a Ryzen 3600 for $170, now it's hovering around $200 and that's one of the chips that hasn't risen dramatically - I can't even look at current-gen chip prices.
  • Deicidium369 - Wednesday, February 3, 2021 - link

    Well Alder Lake - desktop - is likely to be PCIe5 internally (say x16) that presents as 32 PCIe4 lanes - I seriously doubt that there will be a PCIe5 slot on consumer motherboards.
  • JayNor - Wednesday, February 10, 2021 - link

    what about the Alder Lake PCIE5 leaks?
  • Duncan Macdonald - Wednesday, February 3, 2021 - link

    Given the delays on almost all of Intel's plans - will Intel have PCIe 5.0 CPUs in significant numbers before AMD does ? (How many years late are Intel's 7nm offerings ?)
  • shabby - Wednesday, February 3, 2021 - link

    Sure... when pigs fly.

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