The ASUS RS500A-E11-RS12U is an AMD EPYC 7003 (Milan) 1U single-socket server (barebone) that supports up to 16x DIMM, 12x NVMe, 3x PCIe 4.0 slots, 1x OCP 3.0, 2x M.2 and ASUS ASMB10-iKVM and in use for the # vikings hosting platform. It contains the ASUS KRPA-U16 mainboard.

PCIe Gen4 x16,slots, LP (x16 link)                           
          ▲                                                  
          │PCIe Gen4 x16 slot, LP (x8 link)                  
          │            ▲                                     
          └┐           │  PCIe Gen4 x16 slot, FHHL (x16 link)
           │           │                       ▲             
┌────┬────┬┼───────────┼───────────────────────┼─────┐       
│    │    │├─────────┐ ├─────────┐   ┌─────────┴───┐ │       
│    │    │└─────────┘ └─────────┘   └─────────────┘ │       
│ PSU│ PSU│     ┌──┐  ┌───┐            ┌───────────┐ │       
│    │    │ ┌─┐ ├──┘  ├───┘┌──┐┌──┐┌──┐└─────┬─────┘ │       
│    │ ┌──┼─┴─┘ ├──┐  │    │  ││  ││  │      │       │       
│    │ │  │     ├──┘  │    ├──┘├──┘├──┘      │       │       
└────┴─┼──┴─────┼─────▼────┼───┼───┼─────────┼───────┘       
       ▼        ▼    VGA   │   ▼   │         ▼               
 QCode LED  2x USB3.2 Gen1 │ LAN1  ▼   OCP3.0 Gen4 x16       
                           │ 1Gbe LAN2                        
                  BMC ◄────┘      1Gbe                                                         

The mainboard does not support PCIe bifurcation. PCIe cards that internally use multiple controllers requiring bifurcation to achieve full aggregate bandwidth, e.g. Intel E810-XXVDA4 may and e.g. Intel E810-CQDA2 will operate with reduced total throughput. It is recommended to avoid such cards on this mainboard (or ensure they are installed in a sufficiently wide PCIe slot in the case of the Intel E810-XXVDA4 example).

The card has two internal controllers, each requiring x8 lanes. Without bifurcation, both controllers share the x16 slot as a single x16 link, but only one controller is actively used at full speed. The total aggregate bandwidth is limited to approx. 125 Gbps on a PCIe 4.0 x16 slot effective throughput, meaning both ports cannot simultaneously run at full 100 Gbps — only one port at a time can reach line rate.

The ASUS RS500A-E11 provides a PCIe Gen4 x16 Low Profile slot (x16 link), which is the optimal slot for the Intel E810-XXVDA4. Since PCIe Gen4 offers sufficient bandwidth even on a single x8 link, and the slot provides a full x16 link, both internal controllers of the E810-XXVDA4 receive adequate PCIe bandwidth without requiring bifurcation.

All four 25 GbE ports can operate simultaneously at full line rate (4×25 Gbps = 100 Gbps aggregate) without any PCIe bottleneck. Note: If the E810-XXVDA4 were installed in a PCIe x8 slot on this mainboard (which does not support bifurcation), the two internal controllers would share the x8 lanes (x4 each), resulting in a PCIe bottleneck when all four ports are simultaneously under full load. Therefore, installation in the PCIe Gen4 x16 slot is strongly recommended.

When using 4-port network cards in one of the low-profile slots, the server chassis obscures one of the ports by about 0.5 to 1 mm. Inserting a GBIC (or SFP transceiver) is possible with some force, but subsequent removal is very difficult or impossible.

• Potential Fixes
  • When purchasing network cards with 4 slots, use the OCP3.0 or full-height port if possible.
  • For stuck GBICs, gently wiggle while pulling or use a flathead screwdriver for leverage without forcing, to prevent port damage.