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Many motherboards have limited M.2 slots. If you want to add more drives, an expansion card seems like the obvious solution. But here's the common frustration: after plugging it in, the system only recognises the first drive. The rest simply don't show up in Disk Management.

The root cause is almost always PCIe bifurcation. Most multi-drive M.2 expansion cards require a single x4/x8/x16 slot to be split into multiple x2/x4 lanes for multiple devices. This requires the motherboard BIOS to both support and enable the bifurcation setting. Many consumer-grade motherboards do not expose this option, or enabling it may affect lane allocation on other slots. The result: the expansion card is "installed, but not fully usable."

PB65MX3 takes a different approach. It integrates an AMD B650 south bridge chip directly into the PCIe expansion card. The south bridge handles lane splitting and protocol bridging entirely on the card itself, with only a single PCIe 4.0 x4 upstream connection to the host. From the motherboard's perspective, it's just a standard PCIe device — no bifurcation settings required. Plug it in, and all interfaces are recognised immediately.

PB65MX3 ("Big South Bridge") is a PCIe expansion card built around the B650 south bridge chip. Through a single PCIe 4.0 x4 upstream connection, it expands to 4× M.2 NVMe ports, 4× SATA 6Gbps ports, and 4× USB ports (2× USB-A @ 10G, 1× USB-C @ 10G, 1× USB-C @ 20G) — a total of 12 interfaces, providing an all-in-one expansion solution for high-density storage and multiple high-speed peripherals.

Standard multi-drive expansion cards rely on the motherboard to handle PCIe lane splitting, making them dependent on BIOS settings. PB65MX3, however, offloads this work to the onboard B650 south bridge, which handles splitting and bridging entirely on the card. The upstream link is aggregated into a single PCIe 4.0 x4 connection back to the host.

What this means is simple: the motherboard only needs to provide a standard PCIe 4.0 x4 (or longer x8/x16) slot. No BIOS configuration is required whatsoever. All 12 interfaces are immediately recognised by the system. For users with limited BIOS options — or those who simply don't want to mess with motherboard settings — this is the key differentiator from similar expansion cards.

The M.2 interfaces feature intelligent bandwidth allocation: when only the two front slots are populated, both run at x4 links. When all four slots are populated, all four M.2 interfaces automatically adjust to x2 links.

Total upstream bandwidth is constrained by the single PCIe 4.0 x4 connection, with dynamic scheduling handled by the onboard south bridge. When all four drives are under heavy load simultaneously, the two rear slots — and the overall link — step down to x2.

· Slot: Insert into a PCIe 4.0 x4 or longer (x8/x16) slot. Backward compatible with Gen3/Gen2/Gen1.
· OS Support: Windows, Linux, and macOS are all supported.
· Mounting: Includes low-profile and full-height brackets. Choose the appropriate bracket for your chassis height, and use the included standoffs to secure the card.