As per https://www.skhynix.com/products/computing/view.jsp?info.ramKind=20&info.serialNo=HMT84GR7MMR4A, your DIMM is quad-rank. S2600GZ supports up to 8 ranks per memory channel, so in your case two DIMMs per channel.
For more details, refer to the board Technical Product Specification (TPS), section 3.2.4.
S2600GZ - 24 DIMM slots – 3 DIMMs/Channel – 4 memory channels per processor
8 memory channels total with dual CPU configuration
we have only one DIMM per channel (all DIMMs in blue slots) - this is 4 ranks per channel
at least it must work with 2 quad-rank DIMMs per channel if 8 ranks per channel is limitation
Ahh sorry for the misunderstanding - I thought you were talking about each processor...
Have you tried to install 8 DIMMs on one processor and see if it works?
Yes we try to remove all memory modules from channels E-H
System does not start correctly with more than 4 modules in this configuration
Also we try to start system using only channels A & B - system start correctly only with 2 DIMMs installed in A1 & B1.
If modules installed in A1, A2, A3, B1 then system starts, but modules A1, A2, A3 marked as fault by LEDs and BIOS displays only 32GB of RAM (B1 module).
If modules installed in A1, A2, B1, B2 then system does not start.
So it confirms that the issue is not about total capacity, but each memory channel accepts only one DIMM... Not sure if it's related to the DIMM using DDP (Dual Die Packate) and having "8 internal banks"...
You can also try going into the BIOS and changing
Advanced > System Acoustic and Performance Configuration > DCLTT
See if that helps the boot any.
It's a miracle, it works