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1、The Long Road to Rackscale DisaggregationBob WheelerAnalyst-at-LargeOctober 18,20232QUARTERLY MARKET UPDATE|DECEMBER 18,2019OCP Summit 2023 Future Technologies Initiative In-Server Short-Reach Optical InterconnectsAbout Bob Wheeler Industry analyst for more than 20 yearsJoined The Linley Group in 20
2、01Principal Analyst as well as Publisher of Microprocessor ReportHeaded Comms Semi Market Share and Forecast Reports from 2013Left TechInsights in April 2022(following acquisition of The Linley Group)Marketing roles at AMD in mid-90s Engineering management roles at smaller OEMs Started career as a s
3、oftware engineer3QUARTERLY MARKET UPDATE|DECEMBER 18,2019OCP Summit 2023 Future Technologies Initiative In-Server Short-Reach Optical InterconnectsThe Holy Grail of Disaggregation Storage and networking disaggregation are well establishedVarious architectures deployed in hyperscale data centers Prog
4、ress toward main-memory disaggregation has been slowIntel promoted pooled-memory concepts a decade agoThe Gen-Z Consortium formed in 2016 backed by OEMs and memory vendors Compared with prior efforts,CXL is moving quickly to market4QUARTERLY MARKET UPDATE|DECEMBER 18,2019OCP Summit 2023 Future Techn
5、ologies Initiative In-Server Short-Reach Optical InterconnectsCXL Rides the Ubiquitous PCI Express Reusing the PCIe physical layer is key to adoptionEnables coherency without adding to processor pin countsAdd-in cards and modules use the same slots as PCIe devicesAdding CXL support to server require
6、s only the latest Epyc or Xeon CXL Type 3 devices provide cache-coherent memory expansion CXL.mem protocol uses fixed-length transactions Simplest topologies add 100ns of unloaded access latency5QUARTERLY MARKET UPDATE|DECEMBER 18,2019OCP Summit 2023 Future Technologies Initiative In-Server Short-Re
7、ach Optical InterconnectsCXL on All Servers by 2026-5,000 10,000 15,000 20,000 25,000202220232024202520262027CXL-Enabled Host TAM(k units)CXL 1.1CXL 2.0CXL 3.xSource:Wheelers Network6QUARTERLY MARKET UPDATE|DECEMBER 18,2019OCP Summit 2023 Future Technologies Initiative In-Server Short-Reach Optical
8、InterconnectsCXL-Attached Memory Use CasesSingle-host case fits in server chassisSeveral physical topologies for multi-host caseLarge chassis with backplane like Metas Grand Teton1U compute nodes and separate memory applianceCables connect hosts to appliances CXL ports7QUARTERLY MARKET UPDATE|DECEMB
9、ER 18,2019OCP Summit 2023 Future Technologies Initiative In-Server Short-Reach Optical InterconnectsServer Memory Pooling Challenges Latency is key metric for memory accessEven simplest CXL topology can double latencySoftware must become memory-tier aware to minimize performance impactMetas Transpar
10、ent Page Placement upstreamed to Linux kernel Stranded-memory recovery must improve TCOReduced DRAM cost offset by added cost of CXL componentsThis math doesnt support existing optics pricing(e.g.,AOCs)8QUARTERLY MARKET UPDATE|DECEMBER 18,2019OCP Summit 2023 Future Technologies Initiative In-Server
11、Short-Reach Optical InterconnectsCXL-Fabric Nirvana Standards-based coherent interconnect for GPUsAlternative to proprietary NVlink,xGMI,Xe LinkPeer-to-peer communications added in CXL 3.x True shared fabric-attachedmemory(GFAM)CXL 3.x switches for complextopologies CXL-attached DPUs forshared NICSo
12、urce:CXL Consortium9QUARTERLY MARKET UPDATE|DECEMBER 18,2019OCP Summit 2023 Future Technologies Initiative In-Server Short-Reach Optical InterconnectsCXL TAM Compared With Ethernet Optics(Source:Wheelers Network)(Source:LightCounting)10QUARTERLY MARKET UPDATE|DECEMBER 18,2019OCP Summit 2023 Future T
13、echnologies Initiative In-Server Short-Reach Optical InterconnectsThe Role of Optics Fiber addresses challenges of copper cabling for CXL/PCIeCopper bulk,mass,and bend radius problematic for 16 lanes(x16)Passive-copper reach of 1-2m limits scaling Cost is biggest barrier to adoption for opticsASP for 8x50G VCSEL-based AOC is$400 GPU use cases are still speculativeImproving utilization of costly GPUs has high value$Performance considerations grow with cluster scaleThank You Q&A7726 Gunston Plaza Lorton,VA 22199703.997.9187