Outra maneira de verificar a capacidade máxima de RAM é com dmidecode:
sudo dmidecode -t memory
A saída será algo como isto:
Handle 0x000A, DMI type 16, 15 bytes
Physical Memory Array
Location: System Board Or Motherboard
Use: System Memory
Error Correction Type: None
Maximum Capacity: 2 GB <---- look for this line
Error Information Handle: Not Provided
Number Of Devices: 2