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The price of DDR5 memory is setting new highs these days as demand badly outstrips supply. In a bid to save money, Meta is recovering legacy DDR4 memory from used servers and is installing it into new machines using its in-house developed Vistara ASIC that enables it to connect old memory modules to its latest servers running AMD EPYC 'Turin' processors that only support DDR5 memory.Interestingly, Meta is not the only company developing such a solution. Panmnesia, a startup from South Korea, has developed an off-the-shelf CXL controller and switch that enables servers to attach considerably larger memory pools without extending latency, which differentiates Panmnesia’s solution from competing CXL offerings.Custom ASIC enables DDR4 memory to work with new serversVistara is Meta’s first-gen custom CXL memory expander ASIC designed to attach outdated DDR4 memory to modern servers. The chip implements a CXL 2.0 Type-3 memory expander over a PCIe 5.0 x16 interface and bridges standard DDR4 RDIMMs to host processors. Each ASIC supports two independent 72-bit DDR4 memory channels and can provide up to 256 GB of capacity using 64 GB DIMMs. At present, Meta deploys 128 GB per ASIC using 32 GB DDR4 modules recovered from decommissioned servers.
