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Old 03-21-2008, 10:29 AM   #16
laucian
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LM - long mode..
here is my answer! thanks a lot..
i can't really guess where you have found it!
 
Old 03-21-2008, 03:52 PM   #17
farslayer
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Quote:
Originally Posted by laucian View Post
LM - long mode..
here is my answer! thanks a lot..
i can't really guess where you have found it!
Err google search of course.. CPU flags

7th link down.. "CPU feature flags and their meanings"



That same information is in the Link Pixellany posted as well..
Quite an informative link too btw..
 
Old 03-23-2008, 08:39 AM   #18
laucian
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Code:
dhcppc0:/ # getconf LONG_BIT
32
this was what i was searching for..
sorry again for the raging language, thanks everyone who has tried to reply.
 
Old 03-23-2008, 09:52 AM   #19
johnsfine
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I want to clarify something for the benefit of anyone with similar questions who finds and reads this thread:

Quote:
Originally Posted by laucian View Post
how can i learn how many bits is my CPU?
Quote:
Originally Posted by laucian View Post
example.. you are installing software to a remote machine via ssh. you need to know if the machine 32 or 64 bits.
Quote:
Originally Posted by johnsfine View Post
That's a very different question. You don't want to know if the CPU is 64-bit. You want to know if the Linux kernel is 64-bit.
Quote:
Originally Posted by laucian View Post
Code:
dhcppc0:/ # getconf LONG_BIT
32
this was what i was searching for..
That looks like a good way to find out if the Linux kernel is 32-bit or 64-bit.

The consensus of this thread seems to be that the presence of LM in the list of CPU flags (which you can see in /proc/cpuinfo) is a reliable way to determine whether the CPU is 64-bit (which is not what you wanted to determine, but may be what someone else reading this thread wants).
 
Old 03-23-2008, 09:56 AM   #20
laucian
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thanks for the wonderful clarification.
 
Old 10-14-2013, 12:41 PM   #21
GMitch
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Thanks for not just using Google

Sorry to anyone who just got a notice about a reply to such an old thread, perhaps everyone involved has already learned and grown by now. As a person who found this thread through Google, I wanted to weigh in with a few things.

This was the #1 search result, and the ONLY relevant page I found, when trying to "just use Google" to find out if a processor running in one of my active Linux servers was on a 32 or 64 bit processor. It appears that, early in the thread, a productive line of thought could have been shut down by the supposition that this was too simple a question to bother answering, and I'm thankful it wasn't. It's important to remember that Google results change over time, not always for the better, and soon "just Google it" can become the only answer available through Google if too many questions get answered that way.


However, I also wanted to weigh in on the question at hand, because of my results. As it happens, the machine I was looking at was running a 32-bit version of Linux.. I can't remember its name--some long out-of-support version of Debian. On that system, /cat/proc/cpuinfo definitely DID NOT show the "lm" flag. However, at some point in the process I found "64-bit capable: yes" somewhere in the BIOS info, and decided to install the 64-bit version of Ubuntu, and it worked. In Ubuntu, the "lm" flag now DOES show up in cpuinfo.

So, unfortunately, it seems that, while the presence of this flag may be sufficient evidence that a CPU is 64-bit architecture, its absence is NOT a reliable determinant of a 32-bit processor.

Unfortunately, I did not run that getconf LONG_BIT command on the old installation before its drives completely failed, so I don't know if that could have given me any useful info. Since "clflush size" was 64 in both instances, I *would* suppose that it was a determinant quality, if not for:
Quote:
Originally Posted by laucian View Post
it has nothing to do with the bit-model of the cpu. I have a 32-bit Pentium M 735 CPU at home, i ran /proc/cpuinfo and guess what came out..clflush size = 64!!!
For the record, here's the raw results, run on the same machine (I found that Hyperthreading was disabled in the same place in the BIOS I finally found info about the CPU, and enabled it, but just to be completely clear, there was NOT any BIOS setting with which I changed anything else about the processor architecture or instruction set.. with the possible exception of ACPI. Other than those BIOS settings, the only thing that has changed between the two iterations is the HDDs and OS.)
Code:
Linux 2.6.26-2-686 #1 SMP Sun Mar 4 22:19:19 UTC 2012 i686
#cat /proc/cpuinfo 
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 15
model   : 4
model name      : Intel(R) Xeon(TM) CPU 3.80GHz
stepping: 3
cpu MHz : 3800.418
cache size      : 2048 KB
fdiv_bug: no
hlt_bug : no
f00f_bug: no
coma_bug: no
fpu     : yes
fpu_exception   : yes
cpuid level     : 5
wp      : yes
flags   : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts 
pebs bts pni monitor ds_cpl est tm2 cid cx16 xtpr
bogomips: 7606.24
clflush size    : 64
power management:

processor       : 1
vendor_id       : GenuineIntel
cpu family      : 15
model   : 4
model name      : Intel(R) Xeon(TM) CPU 3.80GHz
stepping: 3
cpu MHz : 3800.418
cache size      : 2048 KB
fdiv_bug: no
hlt_bug : no
f00f_bug: no
coma_bug: no
fpu     : yes
fpu_exception   : yes
cpuid level     : 5
wp      : yes
flags   : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts 
pebs bts pni monitor ds_cpl est tm2 cid cx16 xtpr
bogomips: 7600.34
clflush size    : 64
power management:
Code:
Linux 3.8.0-31-generic #46~precise1-Ubuntu SMP Wed Sep 11 18:21:16 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
~$ cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 15
model           : 4
model name      : Intel(R) Xeon(TM) CPU 3.80GHz
stepping        : 3
microcode       : 0x5
cpu MHz         : 3800.156
cache size      : 2048 KB
physical id     : 0
siblings        : 1
core id         : 0
cpu cores       : 1
apicid          : 0
initial apicid  : 0
fpu             : yes
fpu_exception   : yes
cpuid level     : 5
wp              : yes
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 pbe syscall nx lm constant_tsc pebs bts nopl pni dtes64 monitor ds_cpl est tm2 cid cx16 xtpr
bogomips        : 7600.31
clflush size    : 64
cache_alignment : 128
address sizes   : 36 bits physical, 48 bits virtual
power management:

processor       : 1
vendor_id       : GenuineIntel
cpu family      : 15
model           : 4
model name      : Intel(R) Xeon(TM) CPU 3.80GHz
stepping        : 3
microcode       : 0x5
cpu MHz         : 3800.156
cache size      : 2048 KB
physical id     : 3
siblings        : 1
core id         : 0
cpu cores       : 1
apicid          : 6
initial apicid  : 6
fpu             : yes
fpu_exception   : yes
cpuid level     : 5
wp              : yes
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 pbe syscall nx lm constant_tsc pebs bts nopl pni dtes64 monitor ds_cpl est tm2 cid cx16 xtpr
bogomips        : 7600.33
clflush size    : 64
cache_alignment : 128
address sizes   : 36 bits physical, 48 bits virtual
power management:

processor       : 2
vendor_id       : GenuineIntel
cpu family      : 15
model           : 4
model name      : Intel(R) Xeon(TM) CPU 3.80GHz
stepping        : 3
microcode       : 0x5
cpu MHz         : 3800.156
cache size      : 2048 KB
physical id     : 0
siblings        : 1
core id         : 0
cpu cores       : 0
apicid          : 1
initial apicid  : 1
fpu             : yes
fpu_exception   : yes
cpuid level     : 5
wp              : yes
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 pbe syscall nx lm constant_tsc pebs bts nopl pni dtes64 monitor ds_cpl est tm2 cid cx16 xtpr
bogomips        : 7600.31
clflush size    : 64
cache_alignment : 128
address sizes   : 36 bits physical, 48 bits virtual
power management:

processor       : 3
vendor_id       : GenuineIntel
cpu family      : 15
model           : 4
model name      : Intel(R) Xeon(TM) CPU 3.80GHz
stepping        : 3
microcode       : 0x5
cpu MHz         : 3800.156
cache size      : 2048 KB
physical id     : 3
siblings        : 1
core id         : 0
cpu cores       : 0
apicid          : 7
initial apicid  : 7
fpu             : yes
fpu_exception   : yes
cpuid level     : 5
wp              : yes
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 pbe syscall nx lm constant_tsc pebs bts nopl pni dtes64 monitor ds_cpl est tm2 cid cx16 xtpr
bogomips        : 7600.33
clflush size    : 64
cache_alignment : 128
address sizes   : 36 bits physical, 48 bits virtual
power management:
 
Old 10-14-2013, 02:47 PM   #22
johnsfine
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Quote:
Originally Posted by GMitch View Post
some long out-of-support version of Debian.
I guess that must be the explanation.

If you were running a 32-bit build of a version of Linux new enough that the same version (not build) also supported 64-bit then I don't know why the lm flag would be missing.

But displaying the lm flag requires a version of Linux from after the point that developers knew the lm flag existed. An absurdly old version of Linux could not display the lm flag.

How/whether you were running a version that obsolete is hard for me to explain. But I don't have a better guess at why the lm flag was not displayed.
 
Old 10-14-2013, 03:07 PM   #23
GMitch
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That's definitely a reasonable supposition. However, some deep excavation into ancient search histories seems to suggest that I thought the distro was "Lenny".. which seems to match a 2.6.26 kernel (the first line of those paste blocks was actually uname -a,) but from what I can figure out, isn't old enough to explain the lack of an lm flag in and of itself.

I don't know if it's a potential explanation or not, but I have not been around here long enough to rule out the possibility that the system in question might have been built on different hardware. It was running on that machine as long as I knew about it, but that's barely been a couple of years. Is it possible that migrating an installation between marginally compatible processors (perhaps explaining why someone had disabled HT and ACPI in the BIOS of this machine, to make it act/seem more like an ancient predecessor,) might cause this?
 
Old 10-14-2013, 03:14 PM   #24
johnsfine
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That is far too new for my guess to be correct.
Installed and previously running on different hardware doesn't have an effect on this, so that isn't it.

Was Linux running on the bare hardware? If you had some kind of virtual machine host OS installed and Linux installed under that, you could expect the lm flag to be lost as you described.
 
Old 10-14-2013, 03:23 PM   #25
GMitch
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Definitely bare hardware. I can't think of any other details that might make this situation unique..
 
  


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