diff --git a/sys/man/8/plan9.ini b/sys/man/8/plan9.ini
index 9e82444f6..deac7794b 100644
--- a/sys/man/8/plan9.ini
+++ b/sys/man/8/plan9.ini
@@ -730,6 +730,9 @@ processors.
 Prints a summary of the multiprocessor APIC interrupt configuration.
 .SS \fL*nomsi=\fP
 Disables message signaled interrupts.
+.SS \fL*notsc=\fP
+Disables the use of the per processor timestamp counter registers
+as high resolution clock.
 .SS \fL*pcimaxbno=value\fP
 This puts a limit on the maximum bus number probed
 on a PCI bus (default 7).
diff --git a/sys/src/9/pc/archacpi.c b/sys/src/9/pc/archacpi.c
index 24b3245bc..45e3b938d 100644
--- a/sys/src/9/pc/archacpi.c
+++ b/sys/src/9/pc/archacpi.c
@@ -519,7 +519,7 @@ identify(void)
 		return 1;
 	if((cp = getconf("*nomp")) != nil && strcmp(cp, "0") != 0)
 		return 1;
-	if(m->havetsc)
+	if(m->havetsc && getconf("*notsc") == nil)
 		archacpi.fastclock = tscticks;
 	return 0;
 }
diff --git a/sys/src/9/pc/archmp.c b/sys/src/9/pc/archmp.c
index 23cf4fa66..b5eb89805 100644
--- a/sys/src/9/pc/archmp.c
+++ b/sys/src/9/pc/archmp.c
@@ -395,7 +395,7 @@ identify(void)
 		return 1;
 	}
 
-	if(m->havetsc)
+	if(m->havetsc && getconf("*notsc") == nil)
 		archmp.fastclock = tscticks;
 
 	return 0;