diff -Naurp a/arch/i386/Kconfig b/arch/i386/Kconfig
--- a/arch/i386/Kconfig	2006-01-04 15:18:21.000000000 -0800
+++ b/arch/i386/Kconfig	2006-01-19 14:33:33.000000000 -0800
@@ -253,6 +253,20 @@ config X86_UP_IOAPIC
 	  to use it. If you say Y here even though your machine doesn't have
 	  an IO-APIC, then the kernel will still run with no slowdown at all.
 
+config X86_UP_APIC_DEFAULT_OFF
+	bool "APIC support on uniprocessors defaults to off"
+	depends on !SMP && X86_UP_APIC
+	help
+	  Some older systems have flaky APICs.  Say Y to keep leave the APICs
+	  disabled by default, while still allowing them to be enabled by the
+	  "lapic" (local APIC) and "apic" (I/O APIC) command line options.
+	  Generally speaking, either you want to enable both types of APICs
+	  or none at all.
+
+	  Usually this is only necessary for distro installer kernels that
+	  must work with everything.  Everyone else can safely say N here
+	  and configure APIC support in or out as needed.
+
 config X86_LOCAL_APIC
 	bool
 	depends on X86_UP_APIC || ((X86_VISWS || SMP) && !X86_VOYAGER)
diff -Naurp a/arch/i386/kernel/acpi/boot.c b/arch/i386/kernel/acpi/boot.c
--- a/arch/i386/kernel/acpi/boot.c	2006-01-04 15:18:21.000000000 -0800
+++ b/arch/i386/kernel/acpi/boot.c	2006-01-19 14:17:50.000000000 -0800
@@ -37,6 +37,10 @@
 #include <asm/io.h>
 #include <asm/mpspec.h>
 
+#ifdef CONFIG_X86_32
+extern int enable_local_apic __initdata;
+#endif
+
 #ifdef	CONFIG_X86_64
 
 extern void __init clustered_apic_check(void);
@@ -807,6 +811,16 @@ static void __init acpi_process_madt(voi
 #ifdef CONFIG_X86_LOCAL_APIC
 	int count, error;
 
+#ifdef CONFIG_X86_32
+	if (enable_local_apic < 0) {
+		printk(KERN_INFO PREFIX "Local APIC disabled; pass 'lapic' "
+							"to re-enable.\n");
+		return;
+	}
+
+	printk(KERN_INFO PREFIX "Local APIC enabled.\n");
+#endif
+
 	count = acpi_table_parse(ACPI_APIC, acpi_parse_madt);
 	if (count >= 1) {
 
diff -Naurp a/arch/i386/kernel/apic.c b/arch/i386/kernel/apic.c
--- a/arch/i386/kernel/apic.c	2006-01-04 15:18:21.000000000 -0800
+++ b/arch/i386/kernel/apic.c	2006-01-19 14:21:24.000000000 -0800
@@ -42,8 +42,9 @@
 
 /*
  * Knob to control our willingness to enable the local APIC.
+ * -2=default-disable, -1=force-disable, 1=force-enable, 0=automatic
  */
-int enable_local_apic __initdata = 0; /* -1=force-disable, +1=force-enable */
+int enable_local_apic __initdata = (X86_APIC_DEFAULT_OFF ? -2 : 0);
 
 /*
  * Debug level
@@ -757,7 +758,7 @@ static int __init detect_init_APIC (void
 		 * APIC only if "lapic" specified.
 		 */
 		if (enable_local_apic <= 0) {
-			printk("Local APIC disabled by BIOS -- "
+			printk("Local APIC disabled by BIOS (or by default) -- "
 			       "you can enable it with \"lapic\"\n");
 			return -1;
 		}
@@ -839,7 +840,7 @@ void __init init_apic_mappings(void)
 		int i;
 
 		for (i = 0; i < nr_ioapics; i++) {
-			if (smp_found_config) {
+			if (smp_found_config && !skip_ioapic_setup) {
 				ioapic_phys = mp_ioapics[i].mpc_apicaddr;
 				if (!ioapic_phys) {
 					printk(KERN_ERR
@@ -1273,6 +1274,16 @@ int __init APIC_init_uniprocessor (void)
 		return -1;
 
 	/*
+	 * If local apic is off due to config_x86_apic_off option,
+	 * jump out here.
+	 */
+	if (enable_local_apic < -1) {
+		printk(KERN_INFO "Local APIC disabled by default; "
+					"use 'lapic' to enable it.\n");
+		return -1;
+	}
+
+	/*
 	 * Complain if the BIOS pretends there is one.
 	 */
 	if (!cpu_has_apic && APIC_INTEGRATED(apic_version[boot_cpu_physical_apicid])) {
diff -Naurp a/arch/i386/kernel/io_apic.c b/arch/i386/kernel/io_apic.c
--- a/arch/i386/kernel/io_apic.c	2006-01-04 15:18:21.000000000 -0800
+++ b/arch/i386/kernel/io_apic.c	2006-01-17 14:58:30.000000000 -0800
@@ -681,7 +681,7 @@ void fastcall send_IPI_self(int vector)
 #define MAX_PIRQS 8
 static int pirq_entries [MAX_PIRQS];
 static int pirqs_enabled;
-int skip_ioapic_setup;
+int skip_ioapic_setup = X86_APIC_DEFAULT_OFF;
 
 static int __init ioapic_setup(char *str)
 {
diff -Naurp a/arch/i386/kernel/setup.c b/arch/i386/kernel/setup.c
--- a/arch/i386/kernel/setup.c	2006-01-04 15:18:21.000000000 -0800
+++ b/arch/i386/kernel/setup.c	2006-01-19 14:23:38.000000000 -0800
@@ -60,6 +60,10 @@
 #include "setup_arch_pre.h"
 #include <bios_ebda.h>
 
+#ifdef CONFIG_X86_LOCAL_APIC
+extern int enable_local_apic __initdata;
+#endif
+
 /* Forward Declaration. */
 void __init find_max_pfn(void);
 
@@ -865,6 +869,10 @@ static void __init parse_cmdline_early (
 		/* disable IO-APIC */
 		else if (!memcmp(from, "noapic", 6))
 			disable_ioapic_setup();
+		/* enable IO-APIC */
+		else if (!memcmp(from, "apic", 4))
+			enable_ioapic_setup();
+
 #endif /* CONFIG_X86_IO_APIC */
 #endif /* CONFIG_ACPI */
 
@@ -1606,8 +1614,14 @@ void __init setup_arch(char **cmdline_p)
 #endif
 #endif
 #ifdef CONFIG_X86_LOCAL_APIC
-	if (smp_found_config)
-		get_smp_config();
+	if (smp_found_config) {
+		if (enable_local_apic >= 0) {
+			printk(KERN_INFO "LAPIC enabled.\n");
+			get_smp_config();
+		} else {
+			printk(KERN_INFO "LAPIC disabled.\n");
+		}
+	}
 #endif
 
 	register_memory();
diff -Naurp a/include/asm-i386/acpi.h b/include/asm-i386/acpi.h
--- a/include/asm-i386/acpi.h	2006-01-04 15:18:23.000000000 -0800
+++ b/include/asm-i386/acpi.h	2006-01-17 14:58:30.000000000 -0800
@@ -134,6 +134,10 @@ static inline void disable_ioapic_setup(
 {
 	skip_ioapic_setup = 1;
 }
+static inline void enable_ioapic_setup(void)
+{
+	skip_ioapic_setup = 0;
+}
 
 static inline int ioapic_setup_disabled(void)
 {
diff -Naurp a/include/asm-i386/apic.h b/include/asm-i386/apic.h
--- a/include/asm-i386/apic.h	2006-01-04 15:18:23.000000000 -0800
+++ b/include/asm-i386/apic.h	2006-01-17 14:58:30.000000000 -0800
@@ -82,6 +82,12 @@ int get_physical_broadcast(void);
 # define apic_write_around(x,y) apic_write_atomic((x),(y))
 #endif
 
+#ifdef CONFIG_X86_UP_APIC_DEFAULT_OFF
+# define X86_APIC_DEFAULT_OFF 1
+#else
+# define X86_APIC_DEFAULT_OFF 0
+#endif
+
 static inline void ack_APIC_irq(void)
 {
 	/*