diff --git a/sys/arch/evbmips/cavium/machdep.c b/sys/arch/evbmips/cavium/machdep.c
index 7e6a278dd76b..316764821d95 100644
--- a/sys/arch/evbmips/cavium/machdep.c
+++ b/sys/arch/evbmips/cavium/machdep.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: machdep.c,v 1.19 2020/07/19 06:31:13 simonb Exp $	*/
+/*	$NetBSD: machdep.c,v 1.20 2020/07/19 08:53:24 simonb Exp $	*/
 
 /*
  * Copyright 2001, 2002 Wasabi Systems, Inc.
@@ -114,7 +114,7 @@
 #include "opt_multiprocessor.h"
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.19 2020/07/19 06:31:13 simonb Exp $");
+__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.20 2020/07/19 08:53:24 simonb Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -371,8 +371,10 @@ mach_init_memory(void)
 	physmem = btoc(octeon_btinfo.obt_dram_size * 1024 * 1024);
 
 #ifdef MULTIPROCESSOR
-	const u_int cores = mipsNN_cp0_ebase_read() & MIPS_EBASE_CPUNUM;
-	mem_clusters[0].start = cores * 4096;
+	const uint64_t fuse = octeon_xkphys_read_8(CIU_FUSE);
+	const int cores = popcount64(fuse);
+	mem_clusters[0].start += cores * PAGE_SIZE;
+	mem_clusters[0].size  -= cores * PAGE_SIZE;
 #endif
 
 	/*