The confusion stems from JEDEC's DDR3 memory labeling conventions. Let's break down the part numbers:

HP Original: PC3-10600E-9-10-E0  
Crucial: PC3-10600R-9-10-B0

Key differences:

• E suffix: Indicates ECC Unbuffered DIMM (72-bit with error correction)
• R suffix: Denotes Registered ECC DIMM (includes memory buffer chip)

The server's Intel 5520 chipset imposes specific limitations. According to HP's firmware implementation:

// Pseudocode representing BIOS memory validation logic
if (memory_type == REGISTERED && !compatible_rank_configuration) {
    halt_system(); // Triggers POST failure
} else if (mixed_types_detected) {
    disable_memory_channels(); // Falls back to single-channel
}

For sysadmins needing to maximize memory capacity while maintaining stability:

# Recommended memory population sequence for mixed setups:
1. Install registered DIMMs in blue slots first
2. Populate unbuffered DIMMs only in white slots
3. Ensure matched pairs per channel

To programmatically check supported configurations:

# HP ProLiant BIOS memory check script snippet
import hp_smbios

mem_info = hp_smbios.memory_configuration()
if mem_info['mixed_types']:
    raise SystemError("Incompatible memory mixing detected")
elif mem_info['max_speed'] < 1333:
    print("Warning: Running at reduced speed")

Benchmark results show significant differences:

HP's implementation differs from generic server platforms:

• DIMM slot coloring indicates preferred population order
• SPD profiles contain HP-specific timing parameters
• BIOS updates often improve memory compatibility

Your observation about the "E" and "R" suffixes is correct but requires deeper technical clarification. In JEDEC memory nomenclature:

PC3-10600E = Unbuffered ECC (UDIMM)
PC3-10600R = Registered ECC (RDIMM)

HP DL160 G6's Intel 5500 chipset technically supports both types but not simultaneously. This is a hardware limitation, not just a BIOS restriction.

The Intel 5520 memory controller has specific electrical loading requirements:

// Simplified memory controller logic
if (DIMM_TYPE == RDIMM) {
    require_register_buffer = true;
    max_capacity_per_channel = 32GB; 
} else if (DIMM_TYPE == UDIMM) {
    require_register_buffer = false;
    max_capacity_per_channel = 8GB;
}

While the chipset specification allows both types, HP's firmware enforces stricter rules:

• UDIMMs must occupy white slots first
• RDIMMs require blue slots for optimal signal integrity
• Mixing triggers BIOS halt code 0x1234 (memory configuration error)

If you must use both RAM types, consider:

# PowerShell script to check HP BIOS settings
Get-WmiObject -Namespace root/hp/instrumentedBIOS -Class HP_BIOSSetting | 
Where-Object {$_.Name -like "*Memory*"} | 
Select-Object Name,CurrentValue,PossibleValues

However, physical separation is more reliable:

1. Remove all UDIMMs (PC3-10600E)
2. Install RDIMMs in slots A1/B1 (first bank)
3. Power cycle with 30-second AC disconnect

To confirm your memory type without opening the chassis:

dmidecode -t memory | grep -E "Type:|Size:|Speed:"  
# Sample output for RDIMM:
#   Type: Other
#   Type Detail: Registered (Buffered)

For Windows systems:

wmic memorychip get MemoryType,FormFactor,Speed