ASRock Rack EPC621D4I-2M Motherboard Review

ASRock Rack EPC621D4I 2M
ASRock Rack EPC621D4I 2M

The new ASRock Rack EPC621D4I-2M motherboard we are reviewing here is a truly unique product. Fitting in a small mITX form factor, this platform suited for servers with short depth requirements. Most motherboards in this class would use something along the lines of an Intel Xeon E-2100, Intel Xeon D or Atom CPU. Instead, ASRock Rack fits a massive socket LGA3647 for the Intel Xeon Scalable family. Server platforms using Intel’s mainstream server CPUs in mITX were more common years ago, but ASRock Rack is breaking new ground putting such a large CPU in such a small form factor. As a result, the company needed to make some trade-offs which make the ASRock Rack EPC621D4I-2M an intriguing case study.

ASRock Rack EPC621D4I-2M Motherboard Overview

The ASRock Rack EPC621D4I-2M is an incredibly small motherboard to pack a socket LGA3647 processor. ASRock Rack packs this socket onto a 6.7″ x 6.7″ mITX form factor.

ASRock Rack EPC621D4I 2M Top
ASRock Rack EPC621D4I 2M Top

One can see that the socket absolutely dominates the center of the PCB. Limited space is left over around the edges. That brings us to our first trade-off: memory. ASRock Rack uses SODIMM memory slots in this limited space. Also, ASRock Rack uses four DIMM channels while the Intel Xeon Scalable family is capable of six-channel memory plus up to two DIMMs per channel. Memory capacity is much more constrained in this form factor.

Flipping the motherboard over we see two M.2 (PCIe x4 for NVMe and SATA) slots and additional power circuits that would not fit on the top side. These slots are limited to M.2 2280 (80mm) form factor SSDs and cannot fit M.2 22110 (110mm) SSDs.

ASRock Rack EPC621D4I 2M Bottom
ASRock Rack EPC621D4I 2M Bottom

One drawback to M.2 slots on the bottom of the motherboard is it forces users to pull the entire motherboard out of its case to service the two drives. SSDs today are relatively reliable, and this is an innovative solution to ASRock Rack’s limitation of fitting such a large CPU socket in a small motherboard. Cooling these drives should be given special consideration, as should motherboard standoff spacing.

At the left corner, we see a red SATA port for SATADOM flash drives and a Mini-SAS HD connector. In total, one can use a maximum of seven of the Lewisburg C621 chipset’s fourteen potential SATA III slots when one includes the M.2 slots.

ASRock Rack EPC621D4I 2M Storage Ports
ASRock Rack EPC621D4I 2M Storage Ports

At the very edge of the motherboard, a single PCIe x16 slot is found. We expect most users will use this either for high-speed networking or for a RAID controller. In some cases, one may see a GPU installed. Adding a GPU means one is left with 1GbE networking. We could see it as a desktop, but there are much better consumer options available for desktop form factors.

Power connectors at the right corner of the motherboard barely fit but are manageable.

ASRock Rack EPC621D4I 2M Power Connections
ASRock Rack EPC621D4I 2M Power Connections

We do have to note here that the 24-pin power connector is rotated around so that the locking tab that clips onto the 24-pin power cable is facing the memory slot. To remove the 24-pin power cable one must remove the memory sticks to be able to push the release tab and pull out the power cable.

ASRock Rack EPC621D4I 2M 24 Pin Power Connector
ASRock Rack EPC621D4I 2M 24 Pin Power Connector

I/O outputs at the back of the EPC621D4I-2M are minimal at best with only five ports in total. A large portion of the edge is taken up by the Lewisburg PCH heatsink.

ASRock Rack EPC621D4I 2M Back IO Ports
ASRock Rack EPC621D4I 2M Back IO Ports

Looking at the rear I/O ports, we find:

  • 1x VGA video port
  • 2x RJ-45 ports (the bottom port is used for IPMI)
  • 2x USB 3.1 Gen 1 ports

This is certainly a more minimal configuration as even a dedicated IPMI management port had to be sacrificed to make a small form factor.

From a hardware perspective, the ASRock Rack EPC621D4I-2M certainly had to make a lot of tradeoffs to create a useful platform. We really like some of the innovation ASRock Rack made. Buyers need to be aware though that there are tradeoffs to minimize space.

Before we get on with our testing, we will look at the ASRock Rack EPC621D4I-2M motherboard IPMI and the BIOS.


  1. Pls review ASRock Rack D2143D4I2-2T or Supermicro Edge Computing/Gateway lineup like SuperServer E403-9D-8CN-FN13TP with X11SDW-8C-TP13F.

  2. “We wanted to get this review complete instead of waiting for some of the higher end SKUs like the Intel Xeon Platinum 8280 and Platinum 8276L CPUs available”
    while all of my skylake-sp supports UDIMM, my Cascade-Lake-SP don’t support UDIMM.
    in theory this can’t work…

  3. aus dem ASRock Rack PDF(EPC621D4I-2M – EPC621D6I)
    “4 DIMM slots, Supports Quad Channel DDR4 2993/2666/2400 ECC SO R DIMM, ECC SO DIMM, and non-ECC SO DIMM (Max. 64GB)”
    Es gibt SO R DIMM ????? wo ?

  4. Hello Patrick,
    There is some confusion regarding the ILM of this socket. You mention that it is square and even reference the Dynatron B13. the folks from ASRock Rack and Dynatron were saying that it was a narrow ILM. Can you confirm which type that MB uses?


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