My experience with different RAMs on Titan:
BTW: I know that Titan supports up to 3200, but shouldn’t 3600 memory just run at 3200? Shouldn’t the firmware just read the SPD and set clocks correctly?
I don’t know if the Titan firmware is smart enough. Yes, ideally it should pick the corresponding timing parameters to DDR4-3200, not blindly using the highest DDR4-3600 frequency, if 3600 is not stable. Actually DDR JEDEC frequencies only go as high as DDR4-3200, so 3600 is already considered some sort of overclocking.
FYI, this is how I check my DIMM’s SPD on Titan:
# sudo apt-get install i2c-tools
sudo modprobe i2c-dev ee1004
echo 'ee1004 0x51' | sudo tee /sys/bus/i2c/devices/i2c-0/new_device
echo 'ee1004 0x52' | sudo tee /sys/bus/i2c/devices/i2c-0/new_device
decode-dimms
Output of my CT8G4DFRA32A
# decode-dimms version 4.3
Memory Serial Presence Detect Decoder
By Philip Edelbrock, Christian Zuckschwerdt, Burkart Lingner,
Jean Delvare, Trent Piepho and others
Decoding EEPROM: /sys/bus/i2c/drivers/ee1004/0-0051
Guessing DIMM is in bank 2
Kernel driver used ee1004
---=== SPD EEPROM Information ===---
EEPROM CRC of bytes 0-125 OK (0x8479)
# of bytes written to SDRAM EEPROM 384
Total number of bytes in EEPROM 512
Fundamental Memory type DDR4 SDRAM
SPD Revision 1.1
Module Type UDIMM
EEPROM CRC of bytes 128-253 OK (0x53D8)
---=== Memory Characteristics ===---
Maximum module speed 3200 MT/s (PC4-25600)
Size 8192 MB
Banks x Rows x Columns x Bits 16 x 16 x 10 x 64
SDRAM Device Width 8 bits
Ranks 1
Primary Bus Width 64 bits
AA-RCD-RP-RAS (cycles) 22-22-22-52
Supported CAS Latencies 28T, 26T, 25T, 24T, 23T, 22T, 21T, 20T, 19T, 18T, 17T, 16T, 15T, 14T, 13T, 12T, 11T, 10T
---=== Timings at Standard Speeds ===---
AA-RCD-RP-RAS (cycles) as DDR4-3200 22-22-22-52
AA-RCD-RP-RAS (cycles) as DDR4-2933 21-21-21-47
AA-RCD-RP-RAS (cycles) as DDR4-2666 19-19-19-43
AA-RCD-RP-RAS (cycles) as DDR4-2400 17-17-17-39
AA-RCD-RP-RAS (cycles) as DDR4-2133 15-15-15-35
AA-RCD-RP-RAS (cycles) as DDR4-1866 13-13-13-30
AA-RCD-RP-RAS (cycles) as DDR4-1600 11-11-11-26
---=== Timing Parameters ===---
Minimum Cycle Time (tCKmin) 0.625 ns
Maximum Cycle Time (tCKmax) 1.600 ns
Minimum CAS Latency Time (tAA) 13.750 ns
Minimum RAS to CAS Delay (tRCD) 13.750 ns
Minimum Row Precharge Delay (tRP) 13.750 ns
Minimum Active to Precharge Delay (tRAS) 32.000 ns
Minimum Active to Auto-Refresh Delay (tRC) 45.750 ns
Minimum Recovery Delay (tRFC1) 350.000 ns
Minimum Recovery Delay (tRFC2) 260.000 ns
Minimum Recovery Delay (tRFC4) 160.000 ns
Minimum Four Activate Window Delay (tFAW) 21.000 ns
Minimum Row Active to Row Active Delay (tRRD_S) 2.500 ns
Minimum Row Active to Row Active Delay (tRRD_L) 4.900 ns
Minimum CAS to CAS Delay (tCCD_L) 5.000 ns
Minimum Write Recovery Time (tWR) 15.000 ns
Minimum Write to Read Time (tWTR_S) 2.500 ns
Minimum Write to Read Time (tWTR_L) 7.500 ns
---=== Other Information ===---
Package Type Monolithic
Maximum Activate Count (MAC) Unlimited
Post Package Repair One row per bank group
Soft PPR Supported
Module Nominal Voltage 1.2 V
Thermal Sensor No
---=== Physical Characteristics ===---
Module Height 32 mm
Module Thickness 2 mm front, 1 mm back
Module Reference Card A revision 2
---=== Manufacturer Data ===---
Module Manufacturer Micron Technology
DRAM Manufacturer Micron Technology
Manufacturing Location Code 0x07
Manufacturing Date 2025-W18
Assembly Serial Number 0x4FBE40CA
Part Number CT8G4DFRA32A.8FR1
Revision Code 0x31
Wow, cool, didn’t know that trick yet : )
Here is the output of my M391A4G43BB1-CWEQ:
# decode-dimms version 4.4
Memory Serial Presence Detect Decoder
By Philip Edelbrock, Christian Zuckschwerdt, Burkart Lingner,
Jean Delvare, Trent Piepho and others
Decoding EEPROM: /sys/bus/i2c/drivers/ee1004/0-0052
Guessing DIMM is in bank 3
Kernel driver used ee1004
---=== SPD EEPROM Information ===---
EEPROM CRC of bytes 0-125 OK (0xFD70)
# of bytes written to SDRAM EEPROM 384
Total number of bytes in EEPROM 512
Fundamental Memory type DDR4 SDRAM
SPD Revision 1.1
Module Type UDIMM
EEPROM CRC of bytes 128-253 OK (0xD6A6)
---=== Memory Characteristics ===---
Maximum module speed 3200 MT/s (PC4-25600)
Size 32768 MB
Banks x Rows x Columns x Bits 16 x 17 x 10 x 64
SDRAM Device Width 8 bits
Ranks 2
Rank Mix Symmetrical
Primary Bus Width 64 bits
Bus Width Extension 8 bits
AA-RCD-RP-RAS (cycles) 22-22-22-52
Supported CAS Latencies 24T, 22T, 21T, 20T, 19T, 18T, 17T, 16T, 15T, 14T, 13T, 12T, 11T, 10T
---=== Timings at Standard Speeds ===---
AA-RCD-RP-RAS (cycles) as DDR4-3200 22-22-22-52
AA-RCD-RP-RAS (cycles) as DDR4-2933 21-21-21-47
AA-RCD-RP-RAS (cycles) as DDR4-2666 19-19-19-43
AA-RCD-RP-RAS (cycles) as DDR4-2400 17-17-17-39
AA-RCD-RP-RAS (cycles) as DDR4-2133 15-15-15-35
AA-RCD-RP-RAS (cycles) as DDR4-1866 13-13-13-30
AA-RCD-RP-RAS (cycles) as DDR4-1600 11-11-11-26
---=== Timing Parameters ===---
Minimum Cycle Time (tCKmin) 0.625 ns
Maximum Cycle Time (tCKmax) 1.600 ns
Minimum CAS Latency Time (tAA) 13.750 ns
Minimum RAS to CAS Delay (tRCD) 13.750 ns
Minimum Row Precharge Delay (tRP) 13.750 ns
Minimum Active to Precharge Delay (tRAS) 32.000 ns
Minimum Active to Auto-Refresh Delay (tRC) 45.750 ns
Minimum Recovery Delay (tRFC1) 350.000 ns
Minimum Recovery Delay (tRFC2) 260.000 ns
Minimum Recovery Delay (tRFC4) 160.000 ns
Minimum Four Activate Window Delay (tFAW) 21.000 ns
Minimum Row Active to Row Active Delay (tRRD_S) 2.500 ns
Minimum Row Active to Row Active Delay (tRRD_L) 4.900 ns
Minimum CAS to CAS Delay (tCCD_L) 5.000 ns
Minimum Write Recovery Time (tWR) 15.000 ns
Minimum Write to Read Time (tWTR_S) 2.500 ns
Minimum Write to Read Time (tWTR_L) 7.500 ns
---=== Other Information ===---
Package Type Monolithic
Maximum Activate Count (MAC) Unlimited
Post Package Repair One row per bank group
Soft PPR Supported
Module Nominal Voltage 1.2 V
Thermal Sensor TSE2004 compliant
---=== Physical Characteristics ===---
Module Height 32 mm
Module Thickness 2 mm front, 2 mm back
Module Reference Card E revision 1
---=== Manufacturer Data ===---
Module Manufacturer Samsung
DRAM Manufacturer Samsung
Manufacturing Location Code 0x01
Manufacturing Date 2022-W46
Assembly Serial Number 0x03EB49BC
Part Number M391A4G43BB1-CWE
Looks very similar to yours, which is probably a good sign 
.
BTW: On Fedora, decode-dimms is part of a separate i2c-tools-perl package.
Let me also plug back the old unstable 3600 RAM and run it, so that we have some more data.
Thanks!
Here, what it reports for the two unstable CMN64GX4M2Z3600C18:
# decode-dimms version 4.4
Memory Serial Presence Detect Decoder
By Philip Edelbrock, Christian Zuckschwerdt, Burkart Lingner,
Jean Delvare, Trent Piepho and others
Decoding EEPROM: /sys/bus/i2c/drivers/ee1004/0-0051
Guessing DIMM is in bank 2
Kernel driver used ee1004
---=== SPD EEPROM Information ===---
EEPROM CRC of bytes 0-125 OK (0xF9D2)
# of bytes written to SDRAM EEPROM 384
Total number of bytes in EEPROM 512
Fundamental Memory type DDR4 SDRAM
SPD Revision 1.0
Module Type UDIMM
EEPROM CRC of bytes 128-253 OK (0x27DE)
---=== Memory Characteristics ===---
Maximum module speed 3200 MT/s (PC4-25600)
Size 32768 MB
Banks x Rows x Columns x Bits 16 x 17 x 10 x 64
SDRAM Device Width 8 bits
Ranks 2
Rank Mix Symmetrical
Primary Bus Width 64 bits
AA-RCD-RP-RAS (cycles) 22-22-22-53
Supported CAS Latencies 24T, 23T, 22T, 21T, 20T, 19T, 18T, 17T, 16T, 15T, 14T, 13T, 12T, 11T, 10T, 9T, 8T, 7T
---=== Timings at Standard Speeds ===---
AA-RCD-RP-RAS (cycles) as DDR4-3200 22-22-22-53
AA-RCD-RP-RAS (cycles) as DDR4-2933 21-21-21-49
AA-RCD-RP-RAS (cycles) as DDR4-2666 19-19-19-44
AA-RCD-RP-RAS (cycles) as DDR4-2400 17-17-17-40
AA-RCD-RP-RAS (cycles) as DDR4-2133 15-15-15-36
AA-RCD-RP-RAS (cycles) as DDR4-1866 13-13-13-31
AA-RCD-RP-RAS (cycles) as DDR4-1600 11-11-11-27
---=== Timing Parameters ===---
Minimum Cycle Time (tCKmin) 0.625 ns
Maximum Cycle Time (tCKmax) 1.500 ns
Minimum CAS Latency Time (tAA) 13.740 ns
Minimum RAS to CAS Delay (tRCD) 13.740 ns
Minimum Row Precharge Delay (tRP) 13.740 ns
Minimum Active to Precharge Delay (tRAS) 33.000 ns
Minimum Active to Auto-Refresh Delay (tRC) 46.865 ns
Minimum Recovery Delay (tRFC1) 550.000 ns
Minimum Recovery Delay (tRFC2) 350.000 ns
Minimum Recovery Delay (tRFC4) 260.000 ns
Minimum Four Activate Window Delay (tFAW) 21.000 ns
Minimum Row Active to Row Active Delay (tRRD_S) 3.750 ns
Minimum Row Active to Row Active Delay (tRRD_L) 5.625 ns
Minimum CAS to CAS Delay (tCCD_L) 5.356 ns
---=== Other Information ===---
Package Type Monolithic
Maximum Activate Count (MAC) Unlimited
Post Package Repair Not supported
Module Nominal Voltage 1.2 V
Thermal Sensor TSE2004 compliant
---=== Physical Characteristics ===---
Module Height 32 mm
Module Thickness 2 mm front, 2 mm back
Module Reference Card B revision 0
---=== Manufacturer Data ===---
Module Manufacturer Corsair
DRAM Manufacturer Micron Technology
Part Number CMN64GX4M2Z3600C18
Decoding EEPROM: /sys/bus/i2c/drivers/ee1004/0-0052
Guessing DIMM is in bank 3
Kernel driver used ee1004
---=== SPD EEPROM Information ===---
EEPROM CRC of bytes 0-125 OK (0xF9D2)
# of bytes written to SDRAM EEPROM 384
Total number of bytes in EEPROM 512
Fundamental Memory type DDR4 SDRAM
SPD Revision 1.0
Module Type UDIMM
EEPROM CRC of bytes 128-253 OK (0x27DE)
---=== Memory Characteristics ===---
Maximum module speed 3200 MT/s (PC4-25600)
Size 32768 MB
Banks x Rows x Columns x Bits 16 x 17 x 10 x 64
SDRAM Device Width 8 bits
Ranks 2
Rank Mix Symmetrical
Primary Bus Width 64 bits
AA-RCD-RP-RAS (cycles) 22-22-22-53
Supported CAS Latencies 24T, 23T, 22T, 21T, 20T, 19T, 18T, 17T, 16T, 15T, 14T, 13T, 12T, 11T, 10T, 9T, 8T, 7T
---=== Timings at Standard Speeds ===---
AA-RCD-RP-RAS (cycles) as DDR4-3200 22-22-22-53
AA-RCD-RP-RAS (cycles) as DDR4-2933 21-21-21-49
AA-RCD-RP-RAS (cycles) as DDR4-2666 19-19-19-44
AA-RCD-RP-RAS (cycles) as DDR4-2400 17-17-17-40
AA-RCD-RP-RAS (cycles) as DDR4-2133 15-15-15-36
AA-RCD-RP-RAS (cycles) as DDR4-1866 13-13-13-31
AA-RCD-RP-RAS (cycles) as DDR4-1600 11-11-11-27
---=== Timing Parameters ===---
Minimum Cycle Time (tCKmin) 0.625 ns
Maximum Cycle Time (tCKmax) 1.500 ns
Minimum CAS Latency Time (tAA) 13.740 ns
Minimum RAS to CAS Delay (tRCD) 13.740 ns
Minimum Row Precharge Delay (tRP) 13.740 ns
Minimum Active to Precharge Delay (tRAS) 33.000 ns
Minimum Active to Auto-Refresh Delay (tRC) 46.865 ns
Minimum Recovery Delay (tRFC1) 550.000 ns
Minimum Recovery Delay (tRFC2) 350.000 ns
Minimum Recovery Delay (tRFC4) 260.000 ns
Minimum Four Activate Window Delay (tFAW) 21.000 ns
Minimum Row Active to Row Active Delay (tRRD_S) 3.750 ns
Minimum Row Active to Row Active Delay (tRRD_L) 5.625 ns
Minimum CAS to CAS Delay (tCCD_L) 5.356 ns
---=== Other Information ===---
Package Type Monolithic
Maximum Activate Count (MAC) Unlimited
Post Package Repair Not supported
Module Nominal Voltage 1.2 V
Thermal Sensor TSE2004 compliant
---=== Physical Characteristics ===---
Module Height 32 mm
Module Thickness 2 mm front, 2 mm back
Module Reference Card B revision 0
---=== Manufacturer Data ===---
Module Manufacturer Corsair
DRAM Manufacturer Micron Technology
Part Number CMN64GX4M2Z3600C18
Number of SDRAM DIMMs detected and decoded: 2
Doesn’t look that much different, except it is slightly slower (e.g. 22-22-22-53 vs. 22-22-22-52). Could also just be bad RAM, who knows 
Using a 64GB FURY Beast DDR4-3200 PC4-25600 UDIMM RAM Kit (2x 32GB) - KF432C16BBK2/64 kit I bought when I ordered the board, works flawlessly.