Based on parts list there appears to be four revisions of D3358 motherboard used on Celsius R940 systems.
D3358-A12 GS2 / S26361-D3358-A100
D3358-A13 GS2 / S26361-D3358-A101
D3358-A23 GS1 / S26361-D3358-A200
D3358-A23 GS2 / S26361-D3358-A201
It seems that computers with serial number YM9Nxxxxxxxxxx use newer D3358-A23 GSx motherboard.
Is it possible to upgrade R940 that have older D3358-A1x GS2 motherboard with Xeon E5-26xx v4 processors?
Is it possible to use Xeon E5-46xx v3 processors on any of these motherboards? In my experience dual socket LGA2011-3 based systems can use also quad socket LGA2011-3 processors (E5-46xx v3) but not sure about R940 if it's blocked on BIOS level or not.