Use o comando lscpu.
Exemplo de saída de 32 bits:
$ lscpu
Architecture: i686
CPU op-mode(s): 32-bit
Byte Order: Little Endian
CPU(s): 4
On-line CPU(s) list: 0-3
Thread(s) per core: 4
Core(s) per socket: 1
Socket(s): 1
Vendor ID: GenuineIntel
CPU family: 6
Model: 26
Stepping: 5
CPU MHz: 2260.998
BogoMIPS: 4521.99
L1d cache: 32K
L1i cache: 32K
L2 cache: 256K
L3 cache: 8192K
Exemplo de 64 bits:
$ lscpu
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
CPU(s): 4
Thread(s) per core: 1
Core(s) per socket: 4
CPU socket(s): 1
NUMA node(s): 1
Vendor ID: GenuineIntel
CPU family: 6
Model: 23
Stepping: 6
CPU MHz: 2327.533
Virtualization: VT-x
L1d cache: 32K
L1i cache: 32K
L2 cache: 6144K