Visual Inspection

Perhaps one of the most notable design traits of the ASRock Rack B550D4-4L is that it is using a transposed AM4 socket and memory slots. This type of design allows for optimized airflow when installed into a 1U chassis, due to the positioning of the fans from front to rear (or rear to front) when inserted into this type of system. Despite the transposed sockets, it can easily be installed into a regular ATX chassis, although it would be more favorable to direct the air upwards and exhausting it out of the top, to simulate the natural thermodynamics of airflow. In the top-right hand corner of the board is the 24-pin 12 V ATX motherboard power input, while the board's aesthetic is primarily composed of a standard green PCB and uses small silver heatsinks to cool the CPU section of the power delivery, the SoC section, and the chipset itself.

The ASRock B550D4-4L has plenty of connectivity and headers available for users of all levels. Starting from the bottom left-hand corner, ASRock Rack includes a removable SPI Connector chip with a COM port header, a BMC SMBus header, an external speaker header, and an Intelligent Platform Management Bus Header (IPMB). For users focused on security, ASRock Rack also includes a Trusted Management Platform (TPM) header, with one USB 3.2 G1 Type-A header (two ports), and one USB 2.0 header (two ports). For cooling, there's a total of six 6-pin fan headers, although there are notches in the connectors to allow for the use of 4-pin and 3-pin cooling fans. 

Focusing on the board's PCIe slot area, our sample from ASRock Rack has two taped-up slots, a half-length PCIe, and a smaller PCIe slot. These aren't present on retail models and this indicates that we have likely been shipped a pre-production sample. Looking at what should be there is a full-length PCIe 4.0 x16 slot, and a half-length PCIe 4.0 x4 slot, which both feature metal slot reinforcement. 

Looking at storage capability, the B550D4-4L has just one M.2 slot that operates at PCIe 3.0 x4, which also includes support for SATA drives. Other options for SATA devices include a total of six ports, with four of the SATA ports driven by the chipset and includes support for RAID 0, 1, and 10 arrays, while the other two are powered by an ASMedia ASM1061 SATA controller.

Along the top of the transposed socket, is four transposed memory slots. These slots can accommodate up to 128 GB of system memory, with officially supported speeds of up to DDR4-3200. Both non-ECC and ECC memory are supported by the board, but the support itself is reliant on the processor. Users with Ryzen desktop processors can only use non-ECC DDR4, while users with Ryzen Pro models with Radeon Graphics and PRO technologies can use ECC memory. Using memory outside of the validated specification, such as ECC on regular Ryzen, means your mileage may vary.

Providing remote access and integrated graphics via a D-Sub output on the rear panel is an ASPEED AST2500 BMC controller. Users looking to access the system remotely can do so via a dedicated Realtek RTL8211E Gigabit Ethernet port on the rear panel. The ASPEED AST2500 BMC controller is located on the left-hand side of the board by the PCIe slots.

The power delivery on the B550D4-4L is using premium components but isn't adequately cooled for performance users. It features a 4+2 phase power delivery, which is driven by an Intersil ISL69247 PWM controller, which is capable of handling up to eight channels. The CPU section is located on the opposite side of the board from the SoC area, and ASRock Rack includes four Renesas ISL99390 90 A power stages designed to deliver a maximum of 360 A to the processor. The SoC section is using two Renesas ISL99390 90 A power stages.

One of the interesting aspects of the design is the B550D4-4L has a removable 32 MB BIOS chip. This means users with corrupt BIOS chips can easily replace them with a fresh chip, which is suitable for fast-paced professional environments. The housing itself is comprised of two black plastic clips with hinges that keep the BIOS chip securely in place.

On the rear panel at the far left is a D-Sub (DB15) video output for the BMC controller, with a Serial Port (DB9) also present. In terms of USB, the rear panel includes two USB 3.2 G2 Type-A, and two USB 3.2 G1 Type-A ports. Networking is interesting as the board has five Ethernet ports in total. Four of these are individually controlled by four Intel i210 Gigabit Ethernet controllers, while the fifth is powered by a Realtek RTL8211E Gigabit controller which acts as an access point remotely for the BMC controller. Finishing off the rear panel is a single HDMI 1.4 video output that allows use with integrated Radeon graphics.

What's in The Box

Included in the light, yet effective accessories bundle is a user manual, a single black SATA cable, a rear I/O shield, and an M.2 installation screw.

  • User manual
  • Rear panel I/O shield
  • 1 x SATA cable
  • 1 x M.2 installation screw
ASRock Rack B550D4-4L Overview BIOS And Software
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  • im.thatoneguy - Thursday, May 20, 2021 - link

    Please stop putting 10g ports one servers.

    They're always 10-BaseT which is useless to me. They take up pcie lanes. And 25gb/40gb/100gb is imminently supplanting 10gb.

    It's too late for 10g especially baseT
  • fmyhr - Thursday, May 20, 2021 - link

    Heh. I agree with you about 10-BaseT, SFP+ would be preferable if 10GbE *needs* to be present. I don't have $ or power budget for 25gb/40gb/100gb network... but understand those are requirements for some. I'm curious how your ideal board would allocate its limited PCIe lanes among PCIe slots, M.2 slots, OcuLink,...?
  • bananaforscale - Saturday, May 22, 2021 - link

    10GBase-T uses the same cabling as 1000Base-T, assuming the network was built with any future proofing so you can basically just plug it in. 25GBase-T probably won't happen. 'sides, YOU are not the market. What's useless to you is probably useful for someone. Also besides, you can disable those integrated NICs.
  • mode_13h - Saturday, May 22, 2021 - link

    > 10GBase-T uses the same cabling as 1000Base-T,
    > assuming the network was built with any future proofing

    Depends on when. It might've been built with Cat 6, rather than Cat 6A. And even that has shorter length limitations and requires greater power expenditure than we're used to with Gigabit.

    BTW, there's no such standard as Cat 6e. If you see someone selling cable as Cat 6e, treat it as plain Cat 6, but with a bit more suspicion.
  • Samus - Thursday, May 20, 2021 - link

    I think 2x2.5G would be more appropriate for the target market of this board. Anybody considering 10Gbe is likely on the verge of adopting 25/40/100G anyway, in which case the PCIe slot will be utilized.

    The other head scratcher is why the M2 slot isn’t PCIe 4.0 - the allocation of PCIe lanes to ports on this board is very strange.
  • fmyhr - Thursday, May 20, 2021 - link

    Do you have personal experience running 2.5GbE? I've seen reports of problems using both Intel and Realtek chipsets. Whereas 10GbE is very mature and well-supported. Upside of being "obsolete" :-)

    This board runs the M.2 slot from the B550 chipset, which limits its speed to PCIe 3.0. The upside of this choice is an extra PCIe 4.0 x4 slot from the CPU. Into which you could install an M.2 carrier board if you need your SSD on PCIe 4.0. Personally I'd try bifurcating the PCIe 4.0 x16 slot and running a quad M.2 card there, and whatever other PCIe card in the x4 slot.
  • lightningz71 - Thursday, May 20, 2021 - link

    Does this board even support 4way bifurcation of the PCIe x16 slot?
  • Samus - Friday, May 21, 2021 - link

    The B550 can't bifurcate the x4 slot, but it apparently can the x16 slot. In the case of some boards with multiple PCIe 4.0 NVMe M.2 connectors, they start by cutting the x16 slot bandwidth, then after a third M.2 drive is installed they either totally disable the x4 slot or run the x16 slot at x4, configurable in the BIOS (in the case of the Gigabyte B550 Aurus Master)
  • Samus - Friday, May 21, 2021 - link

    Personally no I'm not running any 2.5G stuff, and based on what you are stating, maybe that's why there hasn't been adoption. I agree going with a mature solution but 2.5G isn't exactly new and by now you'd think the bugs are worked out. 2.5G is, after all, based on a lower handshake of 10Gbe, and at long distances 10Gbe actually negotiates at 2.5G, and I have installed 2.5G cards in the field that connect to 10Gbe ports at 2.5G. It's the damn SFP adapters that are all proprietary with their individual standards so you just need to make those up with whatever chipset the NIC you are connecting has.

    Regarding NVMe on B550, I'm not sure what you are getting at. There have been B550 boards on the market for over a year that have not one, not two, but three native PCIe4 NVMe M.2 slots direct from the chipset. Obviously having many M.2 slots impedes on other PCIe x4\x8\x16 slot bandwidth because the consumer Ryzen's don't offer many lanes. But that doesn't mean this board should leave support out entirely as the M.2 could just cut into the x4 or x16 slot bandwidth.
  • mode_13h - Friday, May 21, 2021 - link

    > Do you have personal experience running 2.5GbE?

    Well, the main benefit is cable length and compatibility. If the speed is fast enough for you, then it seems an attractive option for those with legacy cabling.

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