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MikeOS 1.3.0 (Default branch)
04-09-2008
MikeOS is an operating system for x86 PCs, written entirely in assembler. It's not intended to to become a fully-fledged general purpose OS. Instead, it's designed for learning basic OS design and x86 assembly language. Consequently, it runs in 16-bit mode (for BIOS access) and has very low system requirements. It features rudimentary DOS compatibility. License: BSD License (revised) Changes:|
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CPUID(4) Linux Programmer's Manual CPUID(4) NAME
cpuid - x86 CPUID access device DESCRIPTION
CPUID provides an interface for querying information about the x86 CPU. This device is accessed by lseek (2) or pread (2) to the appropriate CPUID level and reading in chunks of 16 bytes. A larger read size means multiple reads of consecutive levels. The lower 32 bits of the file position is used as the incoming %eax, and the upper 32 bits of the file position as the incoming %ecx, the latter intended for "counting" eax levels like eax=4. This driver uses /dev/cpu/CPUNUM/cpuid, where CPUNUM is the minor number, and on an SMP box will direct the access to CPU CPUNUM as listed in /proc/cpuinfo. This file is protected so that it can only be read by the user root, or members of the group root. NOTES
The CPUID instruction can be directly executed by a program using inline assembler. However this device allows convenient access to all CPUs without changing process affinity. Most of the information in cpuid is reported by the kernel in cooked form either in /proc/cpuinfo or through subdirectories in /sys/devices/system/cpu. Direct CPUID access through this device should only be used in exceptional cases. The cpuid driver is not auto-loaded. On modular kernels you might need to use the following command to load it explicitly before use: $ modprobe cpuid There is no support for CPUID functions that require additional input registers. Very old x86 CPUs don't support CPUID. SEE ALSO
Intel Corporation, Intel 64 and IA-32 Architectures Software Developer's Manual Volume 2A: Instruction Set Reference, A-M, 3-180 CPUID ref- erence. Intel Corporation, Intel Processor Identification and the CPUID Instruction, Application note 485. COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 2009-03-31 CPUID(4)