1 files changed, 15 insertions, 13 deletions
diff --git a/man4/cpuid.4 b/man4/cpuid.4
index 3f7d184..e58e29e 100644
--- a/man4/cpuid.4
+++ b/man4/cpuid.4
@@ -3,19 +3,19 @@
 .\"
 .\" SPDX-License-Identifier: Linux-man-pages-copyleft
 .\"
-.TH cpuid 4 2022-10-30 "Linux man-pages 6.05.01"
+.TH cpuid 4 2024-01-05 "Linux man-pages 6.7"
 .SH NAME
 cpuid \- x86 CPUID access device
 .SH DESCRIPTION
 CPUID provides an interface for querying information about the x86 CPU.
-.PP
+.P
 This device is accessed by
 .BR lseek (2)
 or
 .BR pread (2)
 to the appropriate CPUID level and reading in chunks of 16 bytes.
 A larger read size means multiple reads of consecutive levels.
-.PP
+.P
 The lower 32 bits of the file position is used as the incoming
 .IR %eax ,
 and the upper 32 bits of the file position as the incoming
@@ -24,7 +24,7 @@ the latter is intended for "counting"
 .I eax
 levels like
 .IR eax=4 .
-.PP
+.P
 This driver uses
 .IR /dev/cpu/CPUNUM/cpuid ,
 where
@@ -34,7 +34,7 @@ and on an SMP box will direct the access to CPU
 .I CPUNUM
 as listed in
 .IR /proc/cpuinfo .
-.PP
+.P
 This file is protected so that it can be read only by the user
 .IR root ,
 or members of the group
@@ -44,7 +44,7 @@ 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.
-.PP
+.P
 Most of the information in
 .I cpuid
 is reported by the kernel in cooked form either in
@@ -53,29 +53,31 @@ or through subdirectories in
 .IR /sys/devices/system/cpu .
 Direct CPUID access through this device should only
 be used in exceptional cases.
-.PP
+.P
 The
 .I cpuid
 driver is not auto-loaded.
 On modular kernels you might need to use the following command
 to load it explicitly before use:
-.PP
+.P
 .in +4n
 .EX
 $ modprobe cpuid
 .EE
 .in
-.PP
+.P
 There is no support for CPUID functions that require additional
 input registers.
-.PP
-Very old x86 CPUs don't support CPUID.
+.P
+Early i486 CPUs do not support the CPUID instruction;
+.\" arch/x86/kernel/cpuid.c cpuid_open()
+opening this device for those CPUs fails with EIO.
 .SH SEE ALSO
 .BR cpuid (1)
-.PP
+.P
 Intel Corporation, Intel 64 and IA-32 Architectures
 Software Developer's Manual Volume 2A:
 Instruction Set Reference, A-M, 3-180 CPUID reference.
-.PP
+.P
 Intel Corporation, Intel Processor Identification and
 the CPUID Instruction, Application note 485.