How to tell if the system is 32-bit or 64-bit?

kushalkoolwal · 03-17-2009, 07:54 PM

Suppose somebody gives you a system without any stickers/label/product information and you are able to boot a 2.6.26 (standard 32-bit) kernel on it. Now if would like to know whether this system supports 64-bit (SMP) kernel or not, how can you find that out?

One way is to install a 64 bit kernel and then try to boot from it.

If machines crashes/hangs => Your system is 32-bit
If machines boots successfully => Your system does support 64-bit

Another way is to go to BIOS and try to see the CPU information.

However is there any other way by which you can tell without installing the 64-bit kernel or going into the BIOS?

amani · 03-17-2009, 07:58 PM

dmidecode or lshw from a live 32-bit Linux cd

johnsfine · 03-17-2009, 07:58 PM

cat /proc/cpuinfo | grep flags
Then look at the output carefully to see if lm is there.

My output on a system with dual core 64 bit support. Notice the eighth item from the end.

Code:

flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall lm pni monitor ds_cpl est cid cx16 xtpr
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall lm pni monitor ds_cpl est cid cx16 xtpr

This thread wrecks my confidence in LQ's "Similar Threads" feature, because this question sure has been asked and answered multiple times before and every item I see in "Similar Threads" is a total miss. I'm still sure a few attempts at searching would have found the correct similar threads. Answering again was easier.

kushalkoolwal · 03-17-2009, 08:01 PM

Quote:

Originally Posted by amani

dmidecode or lshw from a live 32-bit Linux cd

What should I look in the output. Is the following sufficient to conclude that our machine is 64-bit?

Code:

debian:~# dmidecode | grep 64
        Installed Size: 64 KB
        Maximum Size: 64 KB
        Total Width: 64 bits
        Data Width: 64 bits
debian:~#

kushalkoolwal · 03-17-2009, 08:02 PM

Quote:

Originally Posted by johnsfine

cat /proc/cpuinfo | grep flags
Then look at the output carefully to see if lm is there.

My output on a system with dual core 64 bit support. Notice the eight item from the end.

Code:

flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall lm pni monitor ds_cpl est cid cx16 xtpr
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall lm pni monitor ds_cpl est cid cx16 xtpr

Yes my system does have "lm" too. What does it stand for?

johnsfine · 03-17-2009, 08:08 PM

Quote:

Originally Posted by kushalkoolwal

Yes my system does have "lm" too. What does it stand for?

Long Mode

So your system could run a 64bit kernel.

amani · 03-17-2009, 08:13 PM

'64-bit capable'

you will find it in the CPU info of dmidecode

kushalkoolwal · 03-17-2009, 08:21 PM

Quote:

Originally Posted by amani

'64-bit capable'

you will find it in the CPU info of dmidecode

Not necessarily, here is my dmidecode CPU output on my 64-bit machine:

Code:

debian:~# dmidecode -t 4
# dmidecode 2.9
SMBIOS 2.4 present.

Handle 0x0004, DMI type 4, 35 bytes
Processor Information
        Socket Designation: U2E1
        Type: Central Processor
        Family: Other
        Manufacturer: Intel
        ID: F9 06 00 00 FF FB EB BF
        Version: Genuine Intel(R) CPU             
        Voltage: 3.3 V
        External Clock: Unknown
        Max Speed: 4096 MHz
        Current Speed: 2200 MHz
        Status: Populated, Enabled
        Upgrade: ZIF Socket
        L1 Cache Handle: 0x0005
        L2 Cache Handle: 0x0006
        L3 Cache Handle: Not Provided
        Serial Number: Not Specified
        Asset Tag: Not Specified
        Part Number: Not Specified
debian:~#