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The ASRock Rack 1U4LW-B650/2L2T is a 1U rackmount barebone built around the micro-ATX B650D4U-2L2T/BCM motherboard. Together, they provide one AM5 CPU socket, four DDR5 ECC/non-ECC UDIMM slots, a PCIe 5.0 expansion layout, one PCIe 5.0 M.2 slot, four SATA ports, dual 10GbE, dual 1GbE, and dedicated IPMI management. The chassis adds four hot-swap 3.5-inch SATA bays and a 400 W 80-PLUS Gold power supply.
What the 1U4LW B650 2L2T actually is
The product name combines two related but distinct ASRock Rack components:
- 1U4LW-B650/2L2T: the 1U rackmount barebone, including the chassis, power supply, drive bays and system-level expansion arrangement.
- B650D4U-2L2T/BCM: the installed micro-ATX server motherboard.
ASRock Rack’s 1U4LW Series User Manual maps the 1U4LW-B650/2L2T configuration to the B650D4U-2L2T board. Treat the board and barebone as a matched platform when planning cooling, risers, power and drive connectivity; a motherboard specification alone does not guarantee compatibility with another 1U chassis.
Specifications at a glance
| Area | B650D4U-2L2T/BCM motherboard | 1U4LW-B650/2L2T system |
|---|---|---|
| CPU socket | One AM5 (LGA1718) socket | Uses the installed AM5 board |
| Supported processors | AMD EPYC 4005/4004 and Ryzen 9000, 8000 and 7000 series | Verify BIOS and cooling suitability for the selected processor |
| Memory | Four DDR5 288-pin DIMM slots, 2DPC; ECC and non-ECC UDIMM | Four DIMM slots listed for the system |
| Board expansion | One PCIe 5.0 x16, one PCIe 5.0 x4 and one PCIe 4.0 x1 | One full-height PCIe 4.0 x16 position is listed |
| Storage | Four SATA 6 Gb/s ports and one M.2 PCIe 5.0 x4 slot | Four hot-swap 3.5-inch SATA bays |
| Networking | Two Broadcom BCM57416 10GbE RJ45 ports, two Intel i210 1GbE RJ45 ports and a dedicated IPMI port | Dual 10GbE and dual 1GbE listed |
| Video | HDMI and DisplayPort | HDMI and DisplayPort listed |
| Board size | Micro-ATX, 9.6 x 9.6 inches (24.4 x 24.4 cm) | Not applicable to the chassis |
| Chassis size | Not applicable | 533.4 x 482.6 x 44.4 mm (21 x 19 x 1.75 inches) |
| Power supply | Depends on the host chassis | 400 W, 80-PLUS Gold |
Maximum memory capacity, PCIe bifurcation behavior, riser wiring and the exact hot-swap backplane implementation are not stated in the listed specifications. Check the current board manual, BIOS notes and chassis documentation before ordering parts.
#1 Best Overall
- Micro-ATX (9.6"x 9.6")
- Support AMD Ryzen 7000 series Processors
- 4 DIMM slots (2DPC), supports DDR5 ECC/non-ECC UDIMM
- 1 PCIe5.0 x16, 1 PCIe5.0 x4, 1 PCIe4.0 x1
- Supports 1 M.2 (PCIe5.0 x4)
CPU compatibility and BIOS checks
Supported CPU families
The B650D4U-2L2T/BCM has one AM5 (LGA1718) socket and lists support for AMD EPYC 4005 and 4004 processors, plus Ryzen 9000, 8000 and 7000 series processors. It is therefore a single-socket platform rather than a dual-CPU server board.
Check firmware before installation
Do not assume that every processor in a listed family will boot on every board revision. Confirm the required BIOS version and the current CPU-support list before installing a newer chip. ASRock Rack states in its 1U4LW Series User Manual: “Because the hardware specifications might be updated, the content of this documentation will be subject to change without notice.” A 1U heatsink and fan arrangement also imposes tighter thermal and height limits than a conventional tower case; the chassis documentation should be checked for the chosen CPU.
Memory: use DDR5 ECC UDIMM, not registered DIMMs
There are four DDR5 288-pin DIMM sockets arranged for 2DPC operation. The board specification lists both ECC and non-ECC UDIMM memory. For a server build, the clearest purchasing description is DDR5 ECC UDIMM.
- Use unbuffered ECC UDIMM modules when ECC error detection and correction is required.
- Do not substitute registered DIMM (RDIMM) or load-reduced DIMM (LRDIMM) memory unless ASRock Rack explicitly lists it for this board; the supplied specification identifies UDIMM support.
- Check the board’s current memory QVL, supported speeds and per-slot population rules before filling all four sockets.
The supplied specifications do not state a maximum supported memory capacity, so that figure should not be inferred from the number of slots.
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- 1U Rackmount with 1, 80-PLUS Gold, 315W PSU
- Single Socket AM5 (LGA 1718), supports AMD Ryzen 7000 series processors
- 4 DIMM slots (2DPC), supports DDR5 ECC/non-ECC UDIMM
- 2 hot-swap 2.5" SATA drive bays
- 1 fixed 3.5" SATA drive bay or 1 Slim ODD
Expansion slots and the 1U riser limitation
What the motherboard provides
The B650D4U-2L2T/BCM exposes one PCIe 5.0 x16 slot, one PCIe 5.0 x4 slot and one PCIe 4.0 x1 slot. This gives the board more electrical and physical options than the assembled 1U system may expose through its riser.
What the 1U4LW chassis exposes
The 1U4LW product specification lists one full-height PCIe 4.0 x16 position for the assembled system. In practical terms, a card installed in the barebone should be planned around that chassis-level PCIe 4.0 x16 path, not around the motherboard’s unused PCIe 5.0 slots. Confirm the supplied riser, bracket orientation, card length, card height and airflow clearance before purchasing an adapter, accelerator or storage card.
PCIe bifurcation support is not stated in the supplied material. If a riser or adapter depends on bifurcation, verify it in the current BIOS and board documentation.
Storage planning: one NVMe slot and four SATA bays
M.2 NVMe
The motherboard has one M.2 slot supporting PCIe 5.0 x4. A PCIe 5.0 x4 M.2 NVMe SSD is the directly matched accessory category. This is one M.2 position, not multiple onboard NVMe sockets.
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- Micro-ATX (9.6" x 9.6")
- Supports 12th & 13th Gen Intel Core series processors
- 4 DIMM slots (2DPC), supports DDR5 ECC/non-ECC UDIMM
- 1 PCIe5.0 x16, 1 PCIe4.0 x4, 1 PCIe3.0 x1
- 3 OCuLink (PCIe4.0 x4), 1 OCuLink (PCIe4.0 x4 or 4 SATA 6Gb/s)
SATA and hot-swap drives
Four SATA 6 Gb/s ports are provided on the board, while the 1U4LW chassis adds four hot-swap 3.5-inch SATA bays. The normal planning assumption is that the bays are connected through the board’s SATA ports, but the exact backplane cable and power arrangement should be confirmed against the chassis service documentation before populating all bays.
The listed design therefore combines a boot or fast-working NVMe device with up to four 3.5-inch SATA drives in the chassis, subject to the backplane and cabling arrangement. The specifications do not identify a second M.2 slot or additional onboard SATA controller.
Networking, management and video
Network ports
Two RJ45 ports use the Broadcom BCM57416 10GbE controller, and two additional RJ45 ports use Intel i210 1GbE controllers. This allows separate high-speed data links and lower-speed management, storage or service networks without adding a network card.
IPMI
A dedicated IPMI management port is included. It is physically separate from the four host-network ports, so out-of-band management can remain available when the operating system or primary network configuration is unavailable. The supplied specifications establish the presence of the port but do not detail the firmware feature set or licensing, so consult the current IPMI and BIOS manuals for remote-console, virtual-media and alerting capabilities.
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HDMI and DisplayPort are listed on the motherboard and system pages. These outputs are useful for local setup and troubleshooting; they do not replace IPMI for remote administration.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Will the motherboard fit another rackmount chassis?
The board is micro-ATX and measures 9.6 x 9.6 inches (24.4 x 24.4 cm). That makes the board’s nominal form factor straightforward, but physical compatibility with a different 1U chassis is not automatic. Verify all of the following:
- Micro-ATX standoff locations and board mounting depth.
- Rear-I/O shield alignment and connector access.
- EPS and 24-pin power-connector cable reach.
- AM5 heatsink height, fan duct and front-to-back airflow path.
- Riser type, slot position and full-height card clearance.
- SATA backplane connectors, drive power and hot-swap cabling.
- Front-panel, fan and IPMI wiring.
The matched 1U4LW enclosure is 533.4 x 482.6 x 44.4 mm (21 x 19 x 1.75 inches), the standard 1U height stated by ASRock Rack. Its 400 W 80-PLUS Gold PSU and compact cooling system should be treated as platform limits when selecting a high-power CPU, add-in card or several spinning disks.
Who this platform suits
- Compact virtualization or application servers: the AM5 CPU range, ECC UDIMM option and IPMI are suited to a single-socket host where rack density matters.
- Network-heavy edge systems: dual 10GbE plus dual 1GbE provides four integrated RJ45 links without consuming the expansion position.
- Hybrid NVMe/SATA storage: one PCIe 5.0 x4 M.2 slot can handle an operating-system or cache device while the four hot-swap bays hold SATA disks.
- Space-constrained deployments: the 1U chassis is only 44.4 mm high, but that compactness makes cooling, riser and card-clearance checks essential.
Buying and installation checklist
- Choose a processor from the currently supported EPYC 4005/4004 or Ryzen 9000/8000/7000 lists, then verify its BIOS requirement.
- Buy DDR5 ECC UDIMM memory if server-grade error correction is required; check the current QVL and maximum capacity before ordering.
- Select a PCIe 5.0 x4 M.2 NVMe SSD for the single onboard M.2 slot, and confirm SATA backplane cabling before filling the four hot-swap bays.
- For an add-in card, verify the 1U4LW riser, full-height PCIe 4.0 x16 position, bracket, length, power and airflow requirements.
- Confirm that the 400 W 80-PLUS Gold PSU can support the selected CPU, drives and expansion card.
- Record the current BIOS, board revision and IPMI firmware before deployment, since ASRock Rack warns that specifications and support information can change.
Current pricing, stock, warranty terms and regional availability are not established by the product specifications and should be checked with the seller or systems integrator at the time of purchase.
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