Meta Reuses Old RAM in New Servers with Custom CXL Bridge Chip

Meta developed a custom CXL ASIC called 'Vistara' to address resource waste caused by the mismatch in lifecycle between servers (3-5 years) and memory (7-10 years). This technology allows old DDR4 DIMMs to be connected to the latest DDR5-based servers to expand the memory pool.

Key features of the Vistara ASIC include:

• Support for CXL 2.0/1.1 and PCIe Gen5 x16 interfaces
• Integration of 2 independent 72-bit DDR4 channels per chip (supporting up to 256GB)
• Two internal RISC-V processors

This technology is applied in a device called MemServer, which simultaneously utilizes local DDR5 memory and DDR4 memory via Vistara in systems based on AMD Turin processors. Through this, Meta achieved a reduction of approximately 25% in the number of servers required for memory-intensive workloads such as ML inference (embedding tables, etc.), big data processing, and databases.