I've ran into this before on similar systems. In my case, I updated and rebooted iDrac via the GUI (maintenance>diagnostic) and the 2nd CPU was shown. Hopefully this process works for you.
Hi All, I have searched high and low for a reference to this interesting situation to no avail.  I have a EMC T440 that originally came with  a single Xeon Silver 4110 CPU.  I have since added a second processor - primarily to gain access to the single PCIe x16 slot tied to CPU2.  The processor is functioning just as expected and has even passed every stress-test I have thrown at it. While investigating an issue where installation of a GPU in that aforementioned x16 slot is triggering the chassis fan to ramp up to high-speed unnecessarily, I ventured into iDRAC (I don't really use it that much otherwise).  It is here where the second CPU is detailed (Cores, L1/L2/L3 cache, etc), but indicated to be "Absent" - while CPU1 shows "Presence Detected". Normally, I would just dismiss this since the CPU is functioning as it should where it matters.  But since I am unable to adjust the thermal profile for that slot with the GPU in it, I am starting to wonder if iDRAC's incorrect marking of the presence of the CPU is also leading to issues with the PCIe slot linked to it - and subsequently leading to the issues with setting LFM with the GPU present.  It should be noted, the GPU, a not-officially-supported BUT Dell-branded Radeon is also not detected in iDRAC either.  Since the lone PCIe x16 slot is linked to CPU2, I am starting to think these issues may be related. [IMAGE] CPU2 shows "Absent" [IMAGE] BUT, it details the specs of an "Absent" CPU.   [IMAGE] [IMAGE]   But CPU2 is certainly here - 2 x 16 Threads (8 Physical Cores) = 32.So, any ideas on why iDRAC does't think CPU2 is socketed (but can detail its specs)?  Is there some contact on the socket perhaps that triggers iDRAC's detection of the CPU's presence?  I DID have to slightly modify the heatsink module bracket to get the CPU to socket properly.  And while the CPU if functioning properly, is there some contact switch down there that this modification is failing to trigger perhaps?
Present and *WORKING* CPU showing as absent in iDRAC