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Hmmm, interesting. I wonder what this means for the new Intel Xeon Phi Knights Landing? I liked the approach of many cores on one bootable chip, all having a re

Hmmm, interesting. I wonder what this means for the new Intel Xeon Phi Knights Landing? I liked the approach of many cores on one bootable chip, all having a reasonable amount of local memory, and high bandwidth interconnects: no need to offload data to a peripheral (GPU) device. However with this standard the currently limited bandwidth between peripherals and the main cpu will improve a lot. To me it is obvious why Intel is not joining this party.

convolvatron 10y ago
well, i think its a bit more about market segments and interoperability than anything else. currently overall systems from ibm, and, and intel are fundamentally incompatible. the PCI-E bus that knights landing hangs off of is a qualitatively different thing than the kinds of memory-coherent inter-cpu busses that are being addressed with the CAPI proposal. Intel has their own proprietary QPI. AMD has a quasi-open hyper transport (still?). If this is done properly it means you could make generic motherboards, and generic memory controllers, and all sorts of different accelerators and mix and match them from various vendors. So its no surprise that the smaller players in the market and trying to gang together and the larger player is trying to keep lock-in. Knights Landing as it stands would already integrate in systems better if it were using an inter-cpu bus than a peripheral bus as well as GPUs, FPGAs, and certainly RDMA/memory window systems like Mellanox. Inherent distrust of standards aside, this could be a great win for people putting together bespoke systems in interesting configurations (i.e. Google), I don't think there is any downside in theory for Intel except more competition.
- gpderetta 10y ago
  There are KNL variants that sit on a cpu socket and talk to the rest of the system via QPI.
  - convolvatron 10y ago
    I haven't caught up with the latest phi releases, but I'm really interested to do so. I haven't been able to find any discussion about a coherent QPI on KNL, but have found reference to OmniPath, which looks like a non-coherent large scale memory network. Is that what you were thinking of, or maybe could you post a reference?
    - gpderetta 10y ago
      You are right, I was misremembering. The socketed KNL does not have QPI at all, so no multisocket boards are possible. Still the socketed KNL doesn't hang-off the PCI bus as it is its own host processor and has a dedicated link with memory. Omnipath is used to drive both the Ethernet and PCIe.

convolvatron 10y ago

well, i think its a bit more about market segments and interoperability than anything else. currently overall systems from ibm, and, and intel are fundamentally incompatible. the PCI-E bus that knights landing hangs off of is a qualitatively different thing than the kinds of memory-coherent inter-cpu busses that are being addressed with the CAPI proposal. Intel has their own proprietary QPI. AMD has a quasi-open hyper transport (still?). If this is done properly it means you could make generic motherboards, and generic memory controllers, and all sorts of different accelerators and mix and match them from various vendors. So its no surprise that the smaller players in the market and trying to gang together and the larger player is trying to keep lock-in. Knights Landing as it stands would already integrate in systems better if it were using an inter-cpu bus than a peripheral bus as well as GPUs, FPGAs, and certainly RDMA/memory window systems like Mellanox. Inherent distrust of standards aside, this could be a great win for people putting together bespoke systems in interesting configurations (i.e. Google), I don't think there is any downside in theory for Intel except more competition.

gpderetta 10y ago
There are KNL variants that sit on a cpu socket and talk to the rest of the system via QPI.
- convolvatron 10y ago
  I haven't caught up with the latest phi releases, but I'm really interested to do so. I haven't been able to find any discussion about a coherent QPI on KNL, but have found reference to OmniPath, which looks like a non-coherent large scale memory network. Is that what you were thinking of, or maybe could you post a reference?
  - gpderetta 10y ago
    You are right, I was misremembering. The socketed KNL does not have QPI at all, so no multisocket boards are possible. Still the socketed KNL doesn't hang-off the PCI bus as it is its own host processor and has a dedicated link with memory. Omnipath is used to drive both the Ethernet and PCIe.