1 AMD64 specific boot options
3 There are many others (usually documented in driver documentation), but
4 only the AMD64 specific ones are listed here.
8 mce=off disable machine check
10 nomce (for compatibility with i386): same as mce=off
12 Everything else is in sysfs now.
16 apic Use IO-APIC. Default
17 Unless you have an NVidia or VIA/Uniprocessor board.
18 Then it defaults to off.
20 noapic Don't use the IO-APIC.
22 disableapic Don't use the local APIC
24 nolapic Don't use the local APIC (alias for i386 compatibility)
26 pirq=... See Documentation/i386/IO-APIC.txt
30 syntax: earlyprintk=vga
31 earlyprintk=serial[,ttySn[,baudrate]]
33 The early console is useful when the kernel crashes before the
34 normal console is initialized. It is not enabled by
35 default because it has some cosmetic problems.
36 Append ,keep to not disable it when the real console takes over.
37 Only vga or serial at a time, not both.
38 Currently only ttyS0 and ttyS1 are supported.
39 Interaction with the standard serial driver is not very good.
40 The VGA output is eventually overwritten by the real console.
45 Don't use the CPU time stamp counter to read the wall time.
46 This can be used to work around timing problems on multiprocessor systems
47 with not properly synchronized CPUs. Only useful with a SMP kernel
50 Report when timer interrupts are lost because some code turned off
51 interrupts for too long.
53 nmi_watchdog=NUMBER[,panic]
55 0 don't use an NMI watchdog
56 1 use the IO-APIC timer for the NMI watchdog
57 2 use the local APIC for the NMI watchdog using a performance counter. Note
58 This will use one performance counter and the local APIC's performance
60 When panic is specified panic when an NMI watchdog timeout occurs.
61 This is useful when you use a panic=... timeout and need the box
67 Don't do power saving in the idle loop using HLT, but poll for rescheduling
68 event. This will make the CPUs eat a lot more power, but may be useful
69 to get slightly better performance in multiprocessor benchmarks. It also
70 makes some profiling using performance counters more accurate.
74 reboot=b[ios] | t[riple] | k[bd] [, [w]arm | [c]old]
75 bios Use the CPU reboto vector for warm reset
76 warm Don't set the cold reboot flag
77 cold Set the cold reboto flag
78 triple Force a triple fault (init)
79 kbd Use the keyboard controller. cold reset (default)
81 Using warm reset will be much faster especially on big memory
82 systems because the BIOS will not go through the memory check.
83 Disadvantage is that not all hardware will be completely reinitialized
84 on reboot so there may be boot problems on some systems.
86 Non Executable Mappings
92 noforce (default) Don't enable by default for heap/stack/data,
93 but allow PROT_EXEC to be effective
97 Control the no exec default for 32bit processes.
98 Requires noexec=on or noexec=noforce to be effective.
101 all,on Heap,stack,data is non executable.
102 off (default) Heap,stack,data is executable
103 stack Stack is non executable, heap/data is.
104 force Don't imply PROT_EXEC for PROT_READ
105 compat (default) Imply PROT_EXEC for PROT_READ
109 nosmp Only use a single CPU
111 maxcpus=NUMBER only use upto NUMBER CPUs
113 cpumask=MASK only use cpus with bits set in mask
117 numa=off Only set up a single NUMA node spanning all memory.
122 acpi=off Don't enable ACPI
123 acpi=ht Use ACPI boot table parsing, but don't enable ACPI
125 acpi=force Force ACPI on (currently not needed)
129 pci=off Don't use PCI
130 pci=conf1 Use conf1 access.
131 pci=conf2 Use conf2 access.
133 pci=assign-busses Assign busses
134 pci=irqmask=MASK Set PCI interrupt mask to MASK
135 pci=lastbus=NUMBER Scan upto NUMBER busses, no matter what the mptable says.
139 iommu=[size][,noagp][,off][,force][,noforce][,leak][,memaper[=order]][,soft]
140 size set size of iommu (in bytes)
141 noagp don't initialize the AGP driver and use full aperture.
142 off don't use the IOMMU
143 leak turn on simple iommu leak tracing (only when CONFIG_IOMMU_LEAK is on)
144 memaper[=order] allocate an own aperture over RAM with size 32MB^order.
145 noforce don't force IOMMU usage. Default.
147 soft Use software bounce buffering for non 32bit IO. Default on Intel
152 Prereserve that many 4K pages for the software IO bounce buffering.