Packet Buffer Reference

FS N9600-64OD / N8650-32OD (Broadcom Tomahawk 5)

The FS N9600-64OD and N8650-32OD are 800G-era bare-metal switches built on the Broadcom Tomahawk 5 ASIC (BCM78900 / BCM78902), targeting 51.2 Tbps and 25.6 Tbps AI/ML fabric and hyperscale spine deployments. Both use the OSFP (Octal Small Form-factor Pluggable) transceiver form factor for 800G optics.

Models

Model ASIC Ports Capacity Buffer
N9600-64OD BCM78900 (Tomahawk 5) 64x 800G OSFP, 2x 25G SFP28 51.2 Tbps 165.2 MB
N8650-32OD BCM78902 (Tomahawk 5) 32x 800G OSFP, 2x 25G SFP28 25.6 Tbps ~83 MB (inferred)

Data quality note: The N9600-64OD buffer figure (165.2 MB) is sourced from an FS.com blog publication. The N8650-32OD buffer is inferred by analogy — BCM78902 is the half-capacity Tomahawk 5 variant, and if the same proportional relationship holds as between BCM56990 (113.66 MB) and BCM56993 (56.83 MB), then BCM78902 carries approximately half of 165.2 MB (~82–83 MB). This figure has not been confirmed from an official product datasheet.

Buffer Architecture

The Tomahawk 5 family continues Broadcom's unified shared-buffer architecture. The BCM78900 carries 165.2 MB of on-chip SRAM as a single fully shared pool accessible to all 64 800G ports simultaneously. This represents approximately a 46% increase over the Tomahawk 4's 113.66 MB.

The OSFP form factor supports 800G via 8 lanes of 100G PAM4 or 2 lanes of 400G PAM4, enabling native 800G without external gearboxes when paired with appropriate optics.

The BCM78902 (N8650-32OD) is the half-bandwidth variant, targeting deployments requiring 32-port 800G density at 25.6 Tbps.

References

See Also