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.. SPDX-License-Identifier: GPL-2.0+
.. index::
single: cpuid (command)
cpuid command
=============
Synopsis
--------
::
cpuid <op>
Description
-----------
The cpuid command requests CPU-identification information on x86 CPUs. The
operation <op> selects what information is returned. Up to four 32-bit registers
can be update (eax-edx) depending on the operation.
Configuration
-------------
The cpuid command is only available on x86.
Return value
------------
The return value $? is 0 (true).
Example
-------
::
=> cpuid 1
eax 00060fb1
ebx 00040800
ecx 80002001
edx 178bfbfd
This shows checking for 64-bit 'long' mode::
=> cpuid 80000000
eax 8000000a
ebx 68747541
ecx 444d4163
edx 69746e65
=> cpuid 80000001
eax 00060fb1
ebx 00000000
ecx 00000007
edx 2193fbfd # Bit 29 is set in edx, so long mode is available
On a 32-bit-only CPU::
=> cpuid 80000000
eax 80000004
ebx 756e6547
ecx 6c65746e
edx 49656e69
=> cpuid 80000001
eax 00000663
ebx 00000000
ecx 00000000
edx 00000000 # Bit 29 is not set in edx, so long mode is not available
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