Is it possible to find the physical address range of a DIMM?

Question

I note that SMBios Type 20 would help here, but it's optional as of version 2.5 (2006-09-05) ^{pp. 25, L796, and pp. 131}, whereas types 16, 17 and 19 are mandatory, but don't quite help.

Physical Memory Array (Type 16)

There is one of these structures for the entire system, explaining what is possible on this board.

Handle 0x1000, DMI type 16, 23 bytes
Physical Memory Array
    Location: System Board Or Motherboard
    Use: System Memory
    Error Correction Type: Multi-bit ECC
    Maximum Capacity: 768 GB
    Error Information Handle: Not Provided
    Number Of Devices: 24

Memory Device (Type 17)

There is one record per each Dimm, which tells you the physical Dimms installed on the board.

Handle 0x1100, DMI type 17, 34 bytes
Memory Device
    Array Handle: 0x1000
    Error Information Handle: Not Provided
    Total Width: 72 bits
    Data Width: 64 bits
    Size: 2048 MB
    Form Factor: DIMM
    Set: 1
    Locator: DIMM_A1 
    Bank Locator: Not Specified
    Type: DDR3
    Type Detail: Synchronous Registered (Buffered)
    Speed: 1600 MHz
    Manufacturer: XXXX
    Serial Number: XXXX
    Asset Tag: XXXX
    Part Number: XXXX 
    Rank: 1
    Configured Clock Speed: 1333 MHz

Memory Array Mapped Address (Type 19)

There can be multiple of these records, and each record lists a range of physical addresses.

Here is the output with two 2GB sticks:

Handle 0x1300, DMI type 19, 31 bytes
Memory Array Mapped Address
    Starting Address: 0x00000000000
    Ending Address: 0x000CFFFFFFF
    Range Size: 3328 MB
    Physical Array Handle: 0x1000
    Partition Width: 2

Handle 0x1301, DMI type 19, 31 bytes
Memory Array Mapped Address
    Starting Address: 0x00100000000
    Ending Address: 0x0012FFFFFFF
    Range Size: 768 MB
    Physical Array Handle: 0x1000
    Partition Width: 2

And here is the output with 4 sticks; 2*2GB and 2*4GB:

Handle 0x1300, DMI type 19, 31 bytes
Memory Array Mapped Address
    Starting Address: 0x00000000000
    Ending Address: 0x000CFFFFFFF
    Range Size: 3328 MB
    Physical Array Handle: 0x1000
    Partition Width: 2

Handle 0x1301, DMI type 19, 31 bytes
Memory Array Mapped Address
    Starting Address: 0x00100000000
    Ending Address: 0x0032FFFFFFF
    Range Size: 8960 MB
    Physical Array Handle: 0x1000
    Partition Width: 2

Note that in the first sample output above, there were two 2GB DIMMs, but two ranges of 3.3GB and 0.7GB. With 4 Dimms, the system will also coalesce the memory array mapped address region into two chunks, as it is just representing the same as the e820 map, i.e. the valid memory physical address ranges.

1 to many Type 20 records are tied to exactly one type 17 memory device, meaning that the entire physical range can be known:

Example

$ sudo dmidecode -t 20
# dmidecode 2.12
SMBIOS 2.6 present.

Handle 0x002F, DMI type 20, 19 bytes
Memory Device Mapped Address
    Starting Address: 0x00000000000
    Ending Address: 0x000FFFFFFFF
    Range Size: 4 GB
    Physical Device Handle: 0x002B
    Memory Array Mapped Address Handle: 0x002E
    Partition Row Position: 1

Handle 0x0030, DMI type 20, 19 bytes
Memory Device Mapped Address
    Starting Address: 0x00100000000
    Ending Address: 0x001FFFFFFFF
    Range Size: 4 GB
    Physical Device Handle: 0x002C
    Memory Array Mapped Address Handle: 0x002E
    Partition Row Position: 1

It seems possible to go from address to DIMM for EDAC - Error Detection & Correction purposes, but not from DIMM to entire range.

Looking at the source code of mcelog, it is also using type 20 for its decoding.

Answer 1

which OS you are running? If Linux how abount this command?

grep -i 'System RAM' /proc/iomem    

the first colomn is the physical address;

references: https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/4/html/Reference_Guide/s2-proc-iomem.html https://superuser.com/questions/480451/what-kind-of-memory-addresses-are-the-ones-shown-by-proc-ioports-and-proc-iomem

Answer 2

When you have multiple DIMMS, the BIOS may configure them into some interleave. So you might have one 2G DIMM being physical 0G->4G, bytes 0-7, skipping 8-15. (i.e. low-64 bits) The other 2G DIMM being physical 0G->4G, bytes 8-15, skipping 0-7. (high-64 bits). Note that I think that the interleave is actually bigger than that, because I think that if you have QDR memory, that the system can do 1 address, 8x 64-bit data cycles, so interleaving by units of 64-bytes would be better.

The 0.7G and 3.3G physical arrangements that you see have to do with needing to keep some of the lower 4G open for PCI devices, VGA buffers, classic <1M 8086 crap, etc. This is done by the north bridge. So you have a map like: 0->640K, 1M->3.3G, 0.7G for BIOS, PCI, etc up to 4G. And then 4G->4.7G for ram.

Answer 3

The Brute Force solution seems to be

1. log the memory range of the current configuration
2. power down, remove the DIMM in question and all DIMMs above it
3. reboot, review the new configuration.