Index: sys/powerpc/aim/aim_machdep.c
===================================================================
--- sys/powerpc/aim/aim_machdep.c
+++ sys/powerpc/aim/aim_machdep.c
@@ -113,6 +113,7 @@
 #include <machine/fpu.h>
 #include <machine/hid.h>
 #include <machine/kdb.h>
+#include <machine/machdep.h>
 #include <machine/md_var.h>
 #include <machine/metadata.h>
 #include <machine/mmuvar.h>
@@ -647,8 +648,9 @@
 	mtmsr(msr);
 }
 
+#ifndef __powerpc64__
 void
-cpu_sleep()
+mpc745x_sleep()
 {
 	static u_quad_t timebase = 0;
 	static register_t sprgs[4];
@@ -711,4 +713,5 @@
 		enable_vec(curthread);
 	powerpc_sync();
 }
+#endif
 
Index: sys/powerpc/include/machdep.h
===================================================================
--- sys/powerpc/include/machdep.h
+++ sys/powerpc/include/machdep.h
@@ -37,4 +37,5 @@
 void booke_enable_bpred(void);
 void booke_init_tlb(vm_paddr_t);
 
+void mpc745x_sleep(void);
 #endif /* _POWERPC_MACHDEP_H_ */
Index: sys/powerpc/powermac/platform_powermac.c
===================================================================
--- sys/powerpc/powermac/platform_powermac.c
+++ sys/powerpc/powermac/platform_powermac.c
@@ -45,6 +45,7 @@
 #include <machine/cpu.h>
 #include <machine/fpu.h>	/* For save_fpu() */
 #include <machine/hid.h>
+#include <machine/machdep.h>
 #include <machine/platformvar.h>
 #include <machine/setjmp.h>
 #include <machine/smp.h>
@@ -68,7 +69,9 @@
 static int powermac_smp_start_cpu(platform_t, struct pcpu *cpu);
 static void powermac_smp_timebase_sync(platform_t, u_long tb, int ap);
 static void powermac_reset(platform_t);
+#ifndef __powerpc64__
 static void powermac_sleep(platform_t);
+#endif
 
 static platform_method_t powermac_methods[] = {
 	PLATFORMMETHOD(platform_probe, 		powermac_probe),
@@ -83,7 +86,9 @@
 	PLATFORMMETHOD(platform_smp_timebase_sync, powermac_smp_timebase_sync),
 
 	PLATFORMMETHOD(platform_reset,		powermac_reset),
+#ifndef __powerpc64__
 	PLATFORMMETHOD(platform_sleep,		powermac_sleep),
+#endif
 
 	PLATFORMMETHOD_END
 };
@@ -406,11 +411,18 @@
 	OF_reboot();
 }
 
+#ifndef __powerpc64__
 void
 powermac_sleep(platform_t platform)
 {
+	/* Only supports MPC745x for now. */
+	if (!MPC745X_P(mfspr(SPR_PVR) >> 16)) {
+		printf("sleep only supported for G4 PowerMac hardware.\n");
+		return;
+	}
 
 	*(unsigned long *)0x80 = 0x100;
-	cpu_sleep();
+	mpc745x_sleep();
 }
+#endif