diff --git a/sys/src/9/pc/devarch.c b/sys/src/9/pc/devarch.c
index 2da6f5d55..595cbcb8b 100644
--- a/sys/src/9/pc/devarch.c
+++ b/sys/src/9/pc/devarch.c
@@ -749,7 +749,7 @@ cpuidentify(void)
 	X86type *t, *tab;
 	uintptr cr4;
 	ulong regs[4];
-	vlong mca, mct;
+	vlong mca, mct, pat;
 
 	cpuid(Highstdfunc, regs);
 	memmove(m->cpuidid,   &regs[1], BY2WD);	/* bx */
@@ -882,6 +882,13 @@ cpuidentify(void)
 			rdmsr(0x01, &mct);
 	}
 
+	/* IA32_PAT write combining */
+	if((m->cpuiddx & Pat) != 0 && rdmsr(0x277, &pat) != -1){
+		pat &= ~(255LL<<(PATWC*8));
+		pat |= 1LL<<(PATWC*8);	/* WC */
+		wrmsr(0x277, pat);
+	}
+
 	if(m->cpuiddx & Mtrr)
 		mtrrsync();
 
diff --git a/sys/src/9/pc/mem.h b/sys/src/9/pc/mem.h
index 56649e305..ef646db7d 100644
--- a/sys/src/9/pc/mem.h
+++ b/sys/src/9/pc/mem.h
@@ -173,3 +173,5 @@
 
 #define	getpgcolor(a)	0
 
+/* PAT entry used for write combining */
+#define PATWC	7
diff --git a/sys/src/9/pc/mmu.c b/sys/src/9/pc/mmu.c
index c0b13674a..614339295 100644
--- a/sys/src/9/pc/mmu.c
+++ b/sys/src/9/pc/mmu.c
@@ -66,11 +66,6 @@ static void memglobal(void);
 #define	VPTX(va)		(((ulong)(va))>>12)
 #define	vpd (vpt+VPTX(VPT))
 
-enum {
-	/* PAT entry used for write combining */
-	PATWC	= 7,
-};
-
 void
 mmuinit(void)
 {
@@ -125,14 +120,6 @@ mmuinit(void)
 
 	taskswitch(PADDR(m->pdb),  (ulong)m + BY2PG);
 	ltr(TSSSEL);
-
-	/* IA32_PAT write combining */
-	if((MACHP(0)->cpuiddx & Pat) != 0
-	&& rdmsr(0x277, &v) != -1){
-		v &= ~(255LL<<(PATWC*8));
-		v |= 1LL<<(PATWC*8);	/* WC */
-		wrmsr(0x277, v);
-	}
 }
 
 /* 
diff --git a/sys/src/9/pc64/mem.h b/sys/src/9/pc64/mem.h
index 3a9bf9a1a..c6f9bba70 100644
--- a/sys/src/9/pc64/mem.h
+++ b/sys/src/9/pc64/mem.h
@@ -176,5 +176,8 @@
 
 #define	getpgcolor(a)	0
 
+/* PAT entry used for write combining */
+#define PATWC	7
+
 #define RMACH		R15			/* m-> */
 #define RUSER		R14			/* up-> */
diff --git a/sys/src/9/pc64/mmu.c b/sys/src/9/pc64/mmu.c
index f7c8bb7e5..970d0f262 100644
--- a/sys/src/9/pc64/mmu.c
+++ b/sys/src/9/pc64/mmu.c
@@ -38,9 +38,6 @@ enum {
 	PDE	= 0,
 
 	MAPBITS	= 8*sizeof(m->mmumap[0]),
-
-	/* PAT entry used for write combining */
-	PATWC	= 7,
 };
 
 static void
@@ -133,14 +130,6 @@ mmuinit(void)
 	wrmsr(Star, ((uvlong)UE32SEL << 48) | ((uvlong)KESEL << 32));
 	wrmsr(Lstar, (uvlong)syscallentry);
 	wrmsr(Sfmask, 0x200);
-
-	/* IA32_PAT write combining */
-	if((MACHP(0)->cpuiddx & Pat) != 0
-	&& rdmsr(0x277, &v) != -1){
-		v &= ~(255LL<<(PATWC*8));
-		v |= 1LL<<(PATWC*8);	/* WC */
-		wrmsr(0x277, v);
-	}
 }
 
 /*