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I wanted to do the same thing with PCI!! I thought the bandwidth was large enough that it should be a great direct interface. Unfortunately synchronizing betwee

I wanted to do the same thing with PCI!! I thought the bandwidth was large enough that it should be a great direct interface. Unfortunately synchronizing between two pci masters was going to be tricky and the high frequency development required for PCIe requires some pricey diagnostic equipment. I ran across those off the shelf switches / interfaces, but they were a lot more expensive that 10gb ethernet at the time and they weren't even available for high lane count pcie 2 and pcie 3. I think now that 10gb Ethernet prices are coming down to about $100 per card and switch port there's no way specialized direct pcie would compete off the shelf. Still I think it would be cool to have a direct 32 lane pcie 3 of 4. It could operate as fast as ram speeds. If you connected two 2P beasts it would be close to having a 4P. Of course there would probably be protocol issues and overhead as the no-two-masters issue would mean you can't use the native protocol directly.

nickpsecurity 8y ago
I didnt think about the specialized, diagnostic gear. That couldve priced me out. Far as your other idea, a Distributed, Shared Memory setup was one of my potential applications. I was looking at Beowulf clusters and old MPP systems trying to find ways to get more CPU's with large RAM and simplified programming. I found quite a few software implementations of DSM model. Infiniband and Myrinet were main thing in networking. So, PCI idea was partly about connecting them with something that already had DMA. That at least led me to NUMAscale's products for scaling AMD systems.
- exikyut 8y ago
  Note this comment in this subthread: https://news.ycombinator.com/item?id=17276861 https://news.ycombinator.com/item?id=17276861
namibj 8y ago
Don't worry, the chip you are searching is branded ExpressFabric and sold/made by Broadcom. It's AFAIK only PCIe4, and you get ones with up to iirc 96 lanes per chip. They support to be connected into a mesh, even adding shared PCIe devices like network cards, GPUs, NVMe and SAS/SATA HBAs is possible, though you might have difficulties with the GPUs in particular. The others, if you are careful when buying, should do well if they can handle SR-IOV, as (from their view), the mesh switch they are attached to is the root, and the computers attached to the mesh take the place a VM would normally occupy. If you could get the smallest chip they make, it should not be hard to get a PCB made for it that fans out to e.g. a set of USB-C receptacles. One such receptacle can handle 2 PCIe3 lanes, and some power/USB-2 on the side. The main reason being the relatively low price, compared to e.g. mini SAS HD, which has a similar density and twice the lanes per connector, but also a slightly higher target impedance at the upper end of the PCIe spec, whereas USB-C is specifically targeting the perfect PCIe impedance.
- justinclift 8y ago
  A quick search on Digikey shows several entries for ExpressFabric which seem like what you mean: https://www.digikey.com/products/en?keywords=expressfabric https://www.digikey.com/products/en?keywords=expressfabric They all have a part status of "Discontinued at Digi-Key" though. Not seeing any further info of where they _are_ available either. :/
  - namibj 8y ago
    You found the chips I was referring to. If you want them, you should probably ask Broadcom, as they should either be able to point you to where you can still buy them, or to a replacement. And in case they don't help you, you can still ask sales at competitors, as some might have something suitable. This certainly looks like they'd do a run for you if you want some, albeit with a more significant MOQ (probably in increments of one wafer, with the best price to you if you agree to take all good dies of those they make for you). According to their website [0], they are still active products. It just seems that no one really wants to buy them, due them being somewhat weird. There is a reference platform [1], which is a 32-port, as far as I can tell PCIe3 x4 on QSFP ports, 1U TOR switch. It goes with 2-port cards that go into the servers and contain re-timers. Broadcom claims one can connect the switch with the server cards using optics or copper, but the switch is $11k at mouser. The technology apparently offers virtual Ethernet NICs and 8 QOS classes. Did you want to buy such technology? [0]: https://www.broadcom.com/products/pcie-switches-bridges/expressfabric/#tab-PCIe1 https://www.broadcom.com/products/pcie-switches-bridges/expr... [1]: https://www.broadcom.com/applications/datacenter-networking/expressfabric https://www.broadcom.com/applications/datacenter-networking/... (bottom of the page, grep "ExpressFabric Reference Platform")
    - justinclift 8y ago
      > Did you want to buy such technology? Nope, just merely curious For most of the use cases I can think of that these would suit, Infiniband seems like it would also work and that's fairly widely available already. That being said, there's probably use cases this would suit better. They're just not coming to mind easily. :)

nickpsecurity 8y ago

I didnt think about the specialized, diagnostic gear. That couldve priced me out. Far as your other idea, a Distributed, Shared Memory setup was one of my potential applications. I was looking at Beowulf clusters and old MPP systems trying to find ways to get more CPU's with large RAM and simplified programming. I found quite a few software implementations of DSM model. Infiniband and Myrinet were main thing in networking. So, PCI idea was partly about connecting them with something that already had DMA. That at least led me to NUMAscale's products for scaling AMD systems.

exikyut 8y ago
Note this comment in this subthread: https://news.ycombinator.com/item?id=17276861 https://news.ycombinator.com/item?id=17276861

namibj 8y ago

Don't worry, the chip you are searching is branded ExpressFabric and sold/made by Broadcom. It's AFAIK only PCIe4, and you get ones with up to iirc 96 lanes per chip. They support to be connected into a mesh, even adding shared PCIe devices like network cards, GPUs, NVMe and SAS/SATA HBAs is possible, though you might have difficulties with the GPUs in particular. The others, if you are careful when buying, should do well if they can handle SR-IOV, as (from their view), the mesh switch they are attached to is the root, and the computers attached to the mesh take the place a VM would normally occupy. If you could get the smallest chip they make, it should not be hard to get a PCB made for it that fans out to e.g. a set of USB-C receptacles. One such receptacle can handle 2 PCIe3 lanes, and some power/USB-2 on the side. The main reason being the relatively low price, compared to e.g. mini SAS HD, which has a similar density and twice the lanes per connector, but also a slightly higher target impedance at the upper end of the PCIe spec, whereas USB-C is specifically targeting the perfect PCIe impedance.

justinclift 8y ago
A quick search on Digikey shows several entries for ExpressFabric which seem like what you mean: https://www.digikey.com/products/en?keywords=expressfabric https://www.digikey.com/products/en?keywords=expressfabric They all have a part status of "Discontinued at Digi-Key" though. Not seeing any further info of where they _are_ available either. :/
- namibj 8y ago
  You found the chips I was referring to. If you want them, you should probably ask Broadcom, as they should either be able to point you to where you can still buy them, or to a replacement. And in case they don't help you, you can still ask sales at competitors, as some might have something suitable. This certainly looks like they'd do a run for you if you want some, albeit with a more significant MOQ (probably in increments of one wafer, with the best price to you if you agree to take all good dies of those they make for you). According to their website [0], they are still active products. It just seems that no one really wants to buy them, due them being somewhat weird. There is a reference platform [1], which is a 32-port, as far as I can tell PCIe3 x4 on QSFP ports, 1U TOR switch. It goes with 2-port cards that go into the servers and contain re-timers. Broadcom claims one can connect the switch with the server cards using optics or copper, but the switch is $11k at mouser. The technology apparently offers virtual Ethernet NICs and 8 QOS classes. Did you want to buy such technology? [0]: https://www.broadcom.com/products/pcie-switches-bridges/expressfabric/#tab-PCIe1 https://www.broadcom.com/products/pcie-switches-bridges/expr... [1]: https://www.broadcom.com/applications/datacenter-networking/expressfabric https://www.broadcom.com/applications/datacenter-networking/... (bottom of the page, grep "ExpressFabric Reference Platform")
  - justinclift 8y ago
    > Did you want to buy such technology? Nope, just merely curious For most of the use cases I can think of that these would suit, Infiniband seems like it would also work and that's fairly widely available already. That being said, there's probably use cases this would suit better. They're just not coming to mind easily. :)