.SS \fL*notsc=\fP
Disables the use of the per processor timestamp counter registers
as high resolution clock.
+.SS \fL*nohpet=\fP
+Disables the HPET timer to be used as the high resolution clock.
.SS \fL*pcimaxbno=value\fP
This puts a limit on the maximum bus number probed
on a PCI bus (default 7).
umbexclude=0xD1800-0xD3FFF
.EE
.SS \fL*acpi=\fIvalue\fP
-The presence of this option enables ACPI and the export of the
+This option controls the search for ACPI tables by the kernel.
+The
+.I value
+is the hexadecimal physical address of the RSD structure
+and is passed by the EFI bootloer
+.IR 9boot (8)
+automatically.
+The special
+.I value
+of 1 or empty make the kernel search for the structure
+in BIOS memory area (This is the default).
+The
+special
+.I value
+of 0 will disable ACPI support (for interrupt routing)
+in the kernel,
+but still make table data available in
.B #P/acpitbls
-file in
+file of the
.IR arch (3)
-device. In multiprocessor mode, the kernel will use the ACPI
-tables to configure APIC interrupts unless a
-.I value
-of
-.B 0
-is specified.
+device.
.SS \fLapm0=\fP
This enables the ``advanced power management'' interface
as described in