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HPE Labs manufactures monster memory Machine system

Lars Silver badge

All about the number of bits and hardware like this.

Current 64bit Linux kernel has limit to 64TB of physical RAM and 128TB of virtual memory (see RHEL limits and Debian port). Current x86_64 CPUs (ie. what we have in the PC) has (virtual) address limit 2^48=256TB because of how the address register in the CPU use all the bits (upper bits are used for page flags like ReadOnly, Writable, ExecuteDisable, PagedToDisc etc in the pagetable), but the specification allows to switch to true 64bit address mode reaching the maximum at 2^64=16EB (Exa Bytes). However, the motherboard and CPU die does not have so many pins to deliver all 48 bits of the memory address to the RAM chip through the address bus, so the limit for physical RAM is lower (and depends on manufacturer), but the virtual address space could by nature reach more than the amount of RAM one could have on the motherboard up to virtual memory limit mentioned above.

They receive the 160 TB (40x4) like this:

Each of the 40 nodes consists of two connected boards: a Fabric Attached Memory Board and a compute board. Each Fabric-Attached Memory board consists of four Memory Fabric Controllers, with 4TB of memory per node, and Fabric-Attached Memory. Each compute board consists of a node processor System-on-a-Chip, almost three terabytes per second of aggregate bandwidth, and a local fabric switch.

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