How To Find Out Maximum Supported RAM Or Number Of Available DIMM Slots In Linux

If you need a quick way to find out how much RAM your Linux system supports or to determine the number of DIMM slots available, you can use a command line tool called "dmidecode".

To find out the maximum RAM capacity and the number of RAM slots available, use the following command:

sudo dmidecode -t 16

The output should look something like this:

# dmidecode 2.11
SMBIOS 2.6 present.

Handle 0x0032, DMI type 16, 15 bytes
Physical Memory Array
     Location: System Board Or Motherboard
     Use: System Memory
     Error Correction Type: None
     Maximum Capacity: 16 GB
     Error Information Handle: Not Provided
     Number Of Devices: 4

The "Maximum Capacity" is the maximum RAM supported by your system, while "Number of Devices" is the number of memory (DIMM) slots available on your computer.

To see complete memory information, including the info above along with currently installed memory information (RAM speed, size, etc.), use:

sudo dmidecode -t memory

Here's an example output for the command above:

# dmidecode 2.11
SMBIOS 2.6 present.

Handle 0x0032, DMI type 16, 15 bytes
Physical Memory Array
     Location: System Board Or Motherboard
     Use: System Memory
     Error Correction Type: None
     Maximum Capacity: 16 GB
     Error Information Handle: Not Provided
     Number Of Devices: 4

Handle 0x0033, DMI type 17, 28 bytes
Memory Device
     Array Handle: 0x0032
     Error Information Handle: Not Provided
     Total Width: 64 bits
     Data Width: 64 bits
     Size: 2048 MB
     Form Factor: SODIMM
     Set: None
     Locator: ChannelA-DIMM0
     Bank Locator: BANK 0
     Type: DDR3
     Type Detail: Synchronous
     Speed: 1333 MHz
     Manufacturer: Samsung
     Serial Number: 7732E9D6
     Asset Tag: 9876543210
     Part Number: M471B5773DH0-CH9  
     Rank: Unknown

Handle 0x0035, DMI type 17, 28 bytes
Memory Device
     Array Handle: 0x0032
     Error Information Handle: Not Provided
     Total Width: Unknown
     Data Width: Unknown
     Size: No Module Installed
     Form Factor: DIMM
     Set: None
     Locator: ChannelA-DIMM1
     Bank Locator: BANK 1
     Type: Unknown
     Type Detail: None
     Speed: Unknown
     Manufacturer: Not Specified
     Serial Number: Not Specified
     Asset Tag: 9876543210
     Part Number: Not Specified
     Rank: Unknown

Handle 0x0036, DMI type 17, 28 bytes
Memory Device
     Array Handle: 0x0032
     Error Information Handle: Not Provided
     Total Width: 64 bits
     Data Width: 64 bits
     Size: 4096 MB
     Form Factor: SODIMM
     Set: None
     Locator: ChannelB-DIMM0
     Bank Locator: BANK 2
     Type: DDR3
     Type Detail: Synchronous
     Speed: 1333 MHz
     Manufacturer: 830B
     Serial Number: A74D1715
     Asset Tag: 9876543210
     Part Number: NT4GC64B8HG0NS-CG 
     Rank: Unknown

Handle 0x0038, DMI type 17, 28 bytes
Memory Device
     Array Handle: 0x0032
     Error Information Handle: Not Provided
     Total Width: Unknown
     Data Width: Unknown
     Size: No Module Installed
     Form Factor: DIMM
     Set: None
     Locator: ChannelB-DIMM1
     Bank Locator: BANK 3
     Type: Unknown
     Type Detail: None
     Speed: Unknown
     Manufacturer: Not Specified
     Serial Number: Not Specified
     Asset Tag: 9876543210
     Part Number: Not Specified
     Rank: Unknown

You can also use lshw (among others) for this (firstly, install it; in Ubuntu: "sudo apt-get install lshw):

sudo lshw -C memory

It's important to note that Dmidecode reports system hardware information as described in the BIOS and does not scan your hardware, so in some cases the output can be wrong. Running dmidecode on my Dell XPS L702X non-3D laptop, the output says my system should have 4 RAM slots but in fact there are only 2 and only the 3D version of my laptop can have 4 RAM slots (and by the way, there are some Windows applications reporting the same thing), however, the command is accurate about it supporting 16 GB of RAM.

Also see: How To Get Hardware Information In Linux