diff --git a/sys/src/9/pc/mtrr.c b/sys/src/9/pc/mtrr.c
index 8a4c4565a..03ceea784 100644
--- a/sys/src/9/pc/mtrr.c
+++ b/sys/src/9/pc/mtrr.c
@@ -1,11 +1,3 @@
-/*
- * memory-type region registers.
- *
- * due to the possibility of extended addresses (for PAE)
- * as large as 36 bits coming from the e820 memory map and the like,
- * we'll use vlongs to hold addresses and lengths, even though we don't
- * implement PAE in Plan 9.
- */
 #include "u.h"
 #include "../port/lib.h"
 #include "mem.h"
@@ -20,25 +12,59 @@ enum {
 	 */
 	MTRRPhysBase0 = 0x200,
 	MTRRPhysMask0 = 0x201,
-	MTRRDefaultType = 0x2FF,
-	MTRRCap = 0xFE,
-	Nmtrr = 8,
 
-	/* cpuid extended function codes */
-	Exthighfunc = 1ul << 31,
-	Extprocsigamd,
-	Extprocname0,
-	Extprocname1,
-	Extprocname2,
-	Exttlbl1,
-	Extl2,
-	Extapm,
-	Extaddrsz,
+	MTRRDefaultType = 0x2FF,
+		Deftype = 0xFF,		/* default MTRR type */
+		Deffixena = 1<<10,	/* fixed-range MTRR enable */
+		Defena	= 1<<11,	/* MTRR enable */
+
+	MTRRCap = 0xFE,
+		Capvcnt = 0xFF,		/* mask: # of variable-range MTRRs we have */
+		Capwc = 1<<8,		/* flag: have write combining? */
+		Capfix = 1<<10,		/* flag: have fixed MTRRs? */
+
+	AMDK8SysCfg = 0xC0010010,
+		Tom2Enabled = 1<<21,
+		Tom2ForceMemTypeWB = 1<<22,
+
+	AMDK8TopMem2 = 0xC001001D,
 };
 
 enum {
-	CR4PageGlobalEnable	= 1 << 7,
-	CR0CacheDisable		= 1 << 30,
+	Nvarreg = 8,
+	Nfixreg = 11*8,
+	Nranges = Nfixreg+Nvarreg*2+1,
+};
+
+typedef struct Varreg Varreg;
+struct Varreg {
+	vlong	base;
+	vlong	mask;
+};
+
+typedef struct Fixreg Fixreg;
+struct Fixreg {
+	int	msr;
+	ulong	base;
+	ulong	size;
+};
+
+typedef struct State State;
+struct State {
+	uvlong	mask;
+	vlong	cap;
+	vlong	def;
+	vlong	tom2;
+	int	nvarreg;
+	Varreg	varreg[Nvarreg];
+	vlong	fixreg[Nfixreg/8];
+};
+
+typedef struct Range Range;
+struct Range {
+	uvlong	base;
+	uvlong	size;
+	int	type;
 };
 
 enum {
@@ -51,37 +77,16 @@ enum {
 	Writeback	= 6,
 };
 
-enum {
-	Capvcnt = 0xff,		/* mask: # of variable-range MTRRs we have */
-	Capwc	= 1<<8,		/* flag: have write combining? */
-	Capfix	= 1<<10,	/* flag: have fixed MTRRs? */
-	Deftype = 0xff,		/* default MTRR type */
-	Deffixena = 1<<10,	/* fixed-range MTRR enable */
-	Defena	= 1<<11,	/* MTRR enable */
-};
-
-typedef struct Mtrreg Mtrreg;
-typedef struct Mtrrop Mtrrop;
-
-struct Mtrreg {
-	vlong	base;
-	vlong	mask;
-};
-
 static char *types[] = {
-[Uncacheable]	"uc",
-[Writecomb]	"wc",
-[Unknown1]	"uk1",
-[Unknown2]	"uk2",
-[Writethru]	"wt",
-[Writeprot]	"wp",
-[Writeback]	"wb",
-		nil
+	[Uncacheable]	"uc",
+	[Writecomb]	"wc",
+	[Unknown1]	"uk1",
+	[Unknown2]	"uk2",
+	[Writethru]	"wt",
+	[Writeprot]	"wp",
+	[Writeback]	"wb",
 };
 
-static int dosync;
-static Mtrreg mtrreg[Nmtrr];
-
 static char *
 type2str(int type)
 {
@@ -93,137 +98,635 @@ type2str(int type)
 static int
 str2type(char *str)
 {
-	char **p;
+	int type;
 
-	for(p = types; *p != nil; p++)
-		if (strcmp(str, *p) == 0)
-			return p - types;
+	for(type = 0; type < nelem(types); type++){
+		if(strcmp(str, types[type]) == 0)
+			return type;
+	}
 	return -1;
 }
 
+static int
+getvarreg(State *s, Range *rp, int index)
+{
+	Varreg *reg = &s->varreg[index];
+
+	if((reg->mask & (1<<11)) == 0)
+		return 0;
+	rp->base = reg->base & ~0xFFFULL;
+	rp->type = reg->base & 0xFF;
+	rp->size = (s->mask ^ (reg->mask & ~0xFFFULL)) + 1;
+	return 1;
+}
+
+static void
+setvarreg(State *s, Range *rp, int index)
+{
+	Varreg *reg = &s->varreg[index];
+
+	if(rp == nil || rp->size == 0){
+		reg->base = 0;
+		reg->mask = 0;
+		return;
+	}
+	reg->base = rp->base | (rp->type & 0xFF);
+	reg->mask = (s->mask & ~(rp->size-1)) | 1<<11;
+}
+
+static Fixreg fixreg[Nfixreg/8] = {
+	0x250, 0x00000, 0x10000,
+
+	0x258, 0x80000, 0x04000,
+	0x259, 0xA0000, 0x04000,
+
+	0x268, 0xC0000, 0x01000,
+	0x269, 0xC8000, 0x01000,
+	0x26A, 0xD0000, 0x01000,
+	0x26B, 0xD8000, 0x01000,
+	0x26C, 0xE0000, 0x01000,
+	0x26D, 0xE8000, 0x01000,
+	0x26E, 0xF0000, 0x01000,
+	0x26F, 0xF8000, 0x01000,
+};
+
+static int
+getfixreg(State *s, Range *rp, int index)
+{
+	Fixreg *reg = &fixreg[index >> 3];
+
+	index &= 7;
+	rp->base = reg->base + reg->size * index;
+	rp->size = reg->size;
+	rp->type = ((uvlong)s->fixreg[reg - fixreg] >> 8*index) & 0xFF;
+	return 1;
+}
+
+static void
+setfixreg(State *s, Range *rp, int index)
+{
+	Fixreg *reg = &fixreg[index >> 3];
+	int type;
+
+	index &= 7;
+	if(rp == nil || rp->size == 0)
+		type = Uncacheable;
+	else
+		type = rp->type & 0xFF;
+	s->fixreg[reg - fixreg] &= ~(0xFFULL << 8*index);
+	s->fixreg[reg - fixreg] |= (uvlong)type << 8*index;
+}
+
+static int
+preftype(int a, int b)
+{
+	if(a == b)
+		return a;
+	if(a == Uncacheable || b == Uncacheable)
+		return Uncacheable;
+	if(a == Writethru && b == Writeback
+	|| a == Writeback && b == Writethru)
+		return Writethru;
+	return -1;
+}
+
+static int
+gettype(State *s, uvlong pa, Range *new)
+{
+	int i, type;
+	Range r;
+
+	if(new != nil && pa >= new->base && pa < new->base + new->size)
+		return new->type;
+
+	if((s->def & Defena) == 0)
+		return Uncacheable;
+
+	if(pa < 0x100000 && (s->def & Deffixena) != 0){
+		for(i = 0; i < Nfixreg; i++){
+			if(getfixreg(s, &r, i) && pa < r.base + r.size && pa >= r.base)
+				return r.type;
+		}
+	}
+
+	if(pa >= 0x100000000ULL && pa < s->tom2)
+		return Writeback;
+
+	type = -1;
+	for(i = 0; i < s->nvarreg; i++){
+		if(!getvarreg(s, &r, i))
+			continue;
+		if((pa & -r.size) == r.base)
+			type = (type == -1) ? r.type : preftype(r.type, type);
+	}
+	if(type == -1)
+		type = s->def & Deftype;
+	return type;
+}
+
+static uvlong
+getnext(State *s, uvlong pa, Range *new)
+{
+	uvlong end;
+	Range r;
+	int i;
+
+	if(new != nil){
+		end = getnext(s, pa, nil);
+		if(pa < new->base && end > new->base)
+			return new->base;
+		if(pa < new->base + new->size && end > new->base + new->size)
+			return new->base + new->size;
+		return end;
+	}
+
+	end = s->mask+1;
+	if((s->def & Defena) == 0)
+		return end;
+
+	if(pa < 0x100000 && (s->def & Deffixena) != 0){
+		for(i = 0; i < Nfixreg; i++){
+			if(getfixreg(s, &r, i) && pa < r.base + r.size && pa >= r.base)
+				return r.base + r.size;
+		}
+	}
+
+	if(pa >= 0x100000000ULL && pa < s->tom2)
+		return s->tom2;
+
+	for(i = 0; i < s->nvarreg; i++){
+		if(!getvarreg(s, &r, i))
+			continue;
+		if((pa & -r.size) == r.base)
+			r.base += r.size;
+		else if(r.base <= pa)
+			continue;
+		if(r.base < end)
+			end = r.base;
+	}
+
+	if(pa < 0x100000000ULL && end > 0x100000000ULL)
+		end = 0x100000000ULL;
+
+	return end;
+}
+
+enum {
+	Exthighfunc = 1ul << 31,
+	Extprocsigamd,
+	Extprocname0,
+	Extprocname1,
+	Extprocname2,
+	Exttlbl1,
+	Extl2,
+	Extapm,
+	Extaddrsz,
+};
+
 static uvlong
 physmask(void)
 {
 	ulong regs[4];
-	static vlong mask = -1;
+	uvlong mask;
 
-	if (mask != -1)
-		return mask;
 	cpuid(Exthighfunc, regs);
 	if(regs[0] >= Extaddrsz) {			/* ax */
 		cpuid(Extaddrsz, regs);
-		mask = (1LL << (regs[0] & 0xFF)) - 1;	/* ax */
+		mask = (1ULL << (regs[0] & 0xFF)) - 1;	/* ax */
 	} else {
-		mask &= (1LL << 36) - 1;
+		mask = (1ULL << 36) - 1;
 	}
 	return mask;
 }
 
 static int
-ispow2(uvlong ul)
+getstate(State *s)
 {
-	return (ul & (ul - 1)) == 0;
+	vlong v;
+	int i;
+
+	s->mask = physmask();
+
+	if(rdmsr(MTRRDefaultType, &s->def) < 0)
+		return -1;
+	if(rdmsr(MTRRCap, &s->cap) < 0)
+		return -1;
+
+	if(s->cap & Capfix){
+		for(i = 0; i < nelem(fixreg); i++){
+			if(rdmsr(fixreg[i].msr, &s->fixreg[i]) < 0)
+				return -1;
+		}
+	} else {
+		s->def &= ~(vlong)Deffixena;
+	}
+
+	s->nvarreg = s->cap & Capvcnt;
+	if(s->nvarreg > Nvarreg)
+		s->nvarreg = Nvarreg;
+
+	for(i = 0; i < s->nvarreg; i++){
+		if(rdmsr(MTRRPhysBase0 + 2*i, &s->varreg[i].base) < 0)
+			return -1;
+		if(rdmsr(MTRRPhysMask0 + 2*i, &s->varreg[i].mask) < 0)
+			return -1;
+	}
+
+	if(strcmp(m->cpuidid, "AuthenticAMD") != 0
+	|| m->cpuidfamily < 15
+	|| rdmsr(AMDK8SysCfg, &v) < 0
+	|| (v & (Tom2Enabled|Tom2ForceMemTypeWB)) != (Tom2Enabled|Tom2ForceMemTypeWB)
+	|| rdmsr(AMDK8TopMem2, &s->tom2) < 0)
+		s->tom2 = 0;
+	else {
+		s->tom2 &= s->mask;
+		s->tom2 &= -0x800000LL;
+	}
+
+	return 0;
 }
 
-/* true if mtrr is valid */
-static int
-mtrrdec(Mtrreg *mtrr, uvlong *ptr, uvlong *size, int *type)
-{
-	*ptr =  mtrr->base & ~(BY2PG-1);
-	*type = mtrr->base & 0xff;
-	*size = (physmask() ^ (mtrr->mask & ~(BY2PG-1))) + 1;
-	return (mtrr->mask >> 11) & 1;
-}
+enum {
+	CR4PageGlobalEnable = 1 << 7,
+	CR0CacheDisable = 1 << 30,
+};
 
 static void
-mtrrenc(Mtrreg *mtrr, uvlong ptr, uvlong size, int type, int ok)
+putstate(State *s)
 {
-	mtrr->base = ptr | (type & 0xff);
-	mtrr->mask = (physmask() & ~(size - 1)) | (ok? 1<<11: 0);
-}
-
-/*
- * i is the index of the MTRR, and is multiplied by 2 because
- * mask and base offsets are interleaved.
- */
-static void
-mtrrget(Mtrreg *mtrr, uint i)
-{
-	rdmsr(MTRRPhysBase0 + 2*i, &mtrr->base);
-	rdmsr(MTRRPhysMask0 + 2*i, &mtrr->mask);
-}
-
-static void
-mtrrput(Mtrreg *mtrr, uint i)
-{
-	wrmsr(MTRRPhysBase0 + 2*i, mtrr->base);
-	wrmsr(MTRRPhysMask0 + 2*i, mtrr->mask);
-}
-
-static int
-mtrrvcnt(void)
-{
-	vlong cap;
-	int vcnt;
-
-	rdmsr(MTRRCap, &cap);
-	vcnt = cap & Capvcnt;
-	if(vcnt > Nmtrr)
-		vcnt = Nmtrr;
-	return vcnt;
-}
-
-static int
-mtrrgetall(void)
-{
-	int i, vcnt;
-
-	vcnt = mtrrvcnt();
-	for(i = 0; i < vcnt; i++)
-		mtrrget(&mtrreg[i], i);
-	return vcnt;
-}
-
-static void
-mtrrputall(void)
-{
-	int s, i, vcnt;
 	ulong cr0, cr4;
-	vlong def;
+	int i, x;
 
-	s = splhi();
+	x = splhi();
 
-	cr4 = getcr4();
-	putcr4(cr4 & ~CR4PageGlobalEnable);
+	/* disable cache */
 	cr0 = getcr0();
-	wbinvd();
 	putcr0(cr0 | CR0CacheDisable);
 	wbinvd();
-	rdmsr(MTRRDefaultType, &def);
-	wrmsr(MTRRDefaultType, def & ~(vlong)Defena);
 
-	vcnt = mtrrvcnt();
-	for(i=0; i<vcnt; i++)
-		mtrrput(&mtrreg[i], i);
+	/* disable PGE */
+	cr4 = getcr4();
+	putcr4(cr4 & ~CR4PageGlobalEnable);
 
+	/* flush tlb */
+	putcr3(getcr3());
+
+	/* disable MTRRs */
+	wrmsr(MTRRDefaultType, s->def & ~(vlong)(Defena|Deffixena|Deftype));
 	wbinvd();
-	wrmsr(MTRRDefaultType, def);
+
+	/* write all registers */
+	if(s->cap & Capfix){
+		for(i = 0; i < nelem(fixreg); i++)
+			wrmsr(fixreg[i].msr, s->fixreg[i]);
+	}
+	for(i = 0; i < s->nvarreg; i++){
+		wrmsr(MTRRPhysBase0 + 2*i, s->varreg[i].base);
+		wrmsr(MTRRPhysMask0 + 2*i, s->varreg[i].mask);
+	}
+
+	/* flush tlb */
+	putcr3(getcr3());
+
+	/* enable MTRRs */
+	wrmsr(MTRRDefaultType, s->def);
+
+	/* reenable cache */
 	putcr0(cr0);
+
+	/* reenable PGE */
 	putcr4(cr4);
 
-	splx(s);
+	splx(x);
 }
 
+static int
+fls64(uvlong x)
+{
+	int i;
+
+	for(i = 0; i < 64; i++)
+		if(x & (1ULL<<i))
+			break;
+	return i;
+}
+
+static int
+fms64(uvlong x)
+{
+	int i;
+
+	if(x == 0)
+		return 0;
+	for(i = 63; i >= 0; i--)
+		if(x & (1ULL<<i))
+			break;
+	return i;
+}
+
+static int
+range2varreg(State *s, Range r, int index, int doit)
+{
+	uvlong len;
+
+	if(index < 0)
+		return -1;
+
+	if(r.base <= 0x100000 && (s->def & Deffixena) != 0){
+		r.size += r.base;
+		r.base = 0;
+	}
+
+	if(r.base >= 0x100000000ULL && r.base <= s->tom2){
+		if(r.base + r.size <= s->tom2){
+			if(r.type != Writeback)
+				return -1;
+			return index;
+		}
+	}
+
+	len = r.size;
+	while(len){
+		if(index >= s->nvarreg)
+			return -1;
+		if(fls64(r.base) > fms64(len))
+			r.size = 1ULL << fms64(len);
+		else
+			r.size = 1ULL << fls64(r.base);
+		if(doit)
+			setvarreg(s, &r, index);
+		index++;
+		len -= r.size;
+		r.base += r.size;
+	}
+	return index;
+}
+
+static int ranges2varregs(State*, Range*, int, int, int);
+
+/*
+ * try to combine same type ranges that are split by
+ * higher precedence ranges.
+ */
+static int
+ranges2varregscomb(State *s, Range *rp, int nr, int index, int doit)
+{
+	Range rr;
+	int i, j;
+
+	if(nr < 2 || rp[0].type == rp[1].type)
+		return -1;
+	rr = rp[0];
+	if(preftype(rr.type, rp[1].type) == rr.type)
+		rr.type = rp[1].type;
+	for(j = 1; j < nr; j++){
+		if(rp[j].type != rr.type
+		&& preftype(rp[j].type, rr.type) != rp[j].type)
+			return -1;
+		rr.size += rp[j].size;
+	}
+	i = ranges2varregs(s, &rr, 1, index, doit);
+	for(j = 0; j < nr && i >= index; j++){
+		if(rp[j].type != rr.type)
+			i = range2varreg(s, rp[j], i, doit);
+	}
+	return i;
+}
+
+static int
+ranges2varregs(State *s, Range *rp, int nr, int index, int doit)
+{
+	int i, j, k;
+
+	if(nr == 1){
+		if(rp->type == (s->def & Deftype))
+			return index;
+		return range2varreg(s, *rp, index, doit);
+	}
+
+	/* try combining */
+	i = ranges2varregscomb(s, rp, nr, index, doit);
+
+	/*
+	 * now see if we can find a better solution using
+	 * different splittings.
+	 */
+	for(k = 1; k < nr; k++){
+		j = ranges2varregs(s, rp+k, nr-k,
+			ranges2varregs(s, rp, k, index, 0), 0);
+		if(j < 0)
+			continue;
+		if(i < 0 || j < i)
+			i = doit ? ranges2varregs(s, rp+k, nr-k,
+				ranges2varregs(s, rp, k, index, 1), 1) : j;
+	}
+	return i;
+}
+
+static int
+range2fixreg(State *s, Range r)
+{
+	Range rr;
+	int i;
+
+	for(i = 0; i < Nfixreg; i++){
+		if(!getfixreg(s, &rr, i) || rr.base + rr.size <= r.base)
+			continue;
+		if(rr.base >= r.base + r.size)
+			break;
+		if(r.base > rr.base || r.base + r.size < rr.base + rr.size)
+			return -1;
+		rr.type = r.type;
+		setfixreg(s, &rr, i);
+	}
+	return 0;
+}
+
+static int
+setranges(State *s, Range *rp, int nr)
+{
+	int i, j;
+
+	if(nr < 1 || nr > Nranges)
+		return -1;
+
+	s->def &= ~(vlong)(Defena|Deffixena|Deftype);
+
+	i = 0;
+	if(rp[0].size != s->mask+1 || rp[0].type != Uncacheable){
+		s->def |= Defena;
+
+		/* first handle ranges below 1MB using fixed registers */
+		if(rp[0].size < 0x100000 && (s->cap & Capfix) != 0){
+			s->def |= Deffixena;
+
+			for(i = 0; i < Nfixreg; i++)
+				setfixreg(s, nil, i);
+
+			while(nr > 0 && rp->base < 0x100000){
+				if(range2fixreg(s, *rp) < 0)
+					return -1;
+				if(rp->base + rp->size > 0x100000)
+					break;
+				rp++;
+				nr--;
+			}
+		}
+
+		/* remaining ranges to to variable registers */
+		if(nr > 0){
+			/* make sure the algorithm doesnt explode */
+			if(nr > Nvarreg+1)
+				return -1;
+
+			/* try with UC default type */
+			s->def = (s->def & ~(vlong)Deftype) | Uncacheable;
+			i = ranges2varregs(s, rp, nr, 0, 1);
+
+			/* try with WB default type, dont do it yet */
+			s->def = (s->def & ~(vlong)Deftype) | Writeback;
+			j = ranges2varregs(s, rp, nr, 0, 0);
+			if(j < 0 || (i >= 0 && i <= j)){
+				/* WB not better or worse, use UC solution */
+				s->def = (s->def & ~(vlong)Deftype) | Uncacheable;
+			} else {
+				/* WB default is better, doit! */
+				i = ranges2varregs(s, rp, nr, 0, 1);
+			}
+			if(i < 0)
+				return -1;
+		}
+	}
+
+	/* clear unused variable registers */
+	for(; i < s->nvarreg; i++)
+		setvarreg(s, nil, i);
+
+	return 0;
+}
+
+static int
+checkranges(State *s, Range *rp, int nr)
+{
+	uvlong base, next;
+	int i;
+
+	for(i = 0; i < nr; i++){
+		next = rp[i].base + rp[i].size;
+		for(base = rp[i].base; base < next; base = getnext(s, base, nil)){
+			if(gettype(s, base, nil) != rp[i].type)
+				return -1;
+		}
+	}
+	return 0;
+}
+
+static int
+getranges(State *s, Range *rp, int nr, Range *new)
+{
+	uvlong base, next;
+	Range *rs, *re;
+	int type;
+
+	rs = rp;
+	re = rp + nr;
+	for(base = 0; base <= s->mask; base = next) {
+		if(rp >= re)
+			return -1;
+		type = gettype(s, base, new);
+		next = getnext(s, base, new);
+		while(next <= s->mask && (gettype(s, next, new) == type))
+			next = getnext(s, next, new);
+		rp->base = base;
+		rp->size = next - base;
+		rp->type = type;
+		rp++;
+	}
+	return rp - rs;
+}
+
+static int dosync;
+static QLock mtrrlk;
+static State cpu0state;
+static Range ranges[Nranges];
+
+char*
+mtrr(uvlong base, uvlong size, char *tstr)
+{
+	static State newstate;
+	Range new;
+	int nr;
+
+	if(cpu0state.mask == 0)
+		return "mtrr not supported";
+
+	if(size < 0x1000)
+		return "size too small";
+	if((base | size) & 0xFFF)
+		return "base or size not page aligned";
+	if(base & ~cpu0state.mask)
+		return "base out of range";
+	if(base + size > cpu0state.mask+1)
+		return "size out of range";
+
+	new.base = base;
+	new.size = size;
+	if((new.type = str2type(tstr)) < 0)
+		return "bad cache type";
+
+	qlock(&mtrrlk);
+	newstate = cpu0state;
+	nr = getranges(&newstate, ranges, Nranges, &new);
+	if(setranges(&newstate, ranges, nr) < 0
+	|| checkranges(&newstate, ranges, nr) < 0){
+		qunlock(&mtrrlk);
+		return "cache range not satisfiable";
+	}
+	cpu0state = newstate;
+	coherence();
+	dosync = 1;
+	mtrrclock();
+	qunlock(&mtrrlk);
+
+	return nil;
+}
+
+int
+mtrrprint(char *buf, long bufsize)
+{
+	char *cp, *ep;
+	int i, nr;
+
+	if(cpu0state.mask == 0)
+		return 0;
+
+	cp = buf;
+	ep = buf + bufsize;
+
+	qlock(&mtrrlk);
+	nr = getranges(&cpu0state, ranges, Nranges, nil);
+	for(i = 0; i < nr; i++){
+		cp = seprint(cp, ep, "cache %#.16llux %15llud %s\n",
+			ranges[i].base,
+			ranges[i].size,
+			type2str(ranges[i].type));
+	}
+	qunlock(&mtrrlk);
+
+	return cp - buf;
+}
+
+/* called from clock interrupt */
 void
-mtrrclock(void)				/* called from clock interrupt */
+mtrrclock(void)
 {
 	static Ref bar1, bar2;
-	int s;
+	int x;
 
-	if(dosync == 0)
+	if(dosync == 0 || cpu0state.mask == 0)
 		return;
 
-	s = splhi();
+	x = splhi();
 
 	/*
 	 * wait for all CPUs to sync here, so that the MTRR setup gets
@@ -233,7 +736,7 @@ mtrrclock(void)				/* called from clock interrupt */
 	while(bar1.ref < conf.nmach)
 		microdelay(10);
 
-	mtrrputall();
+	putstate(&cpu0state);
 
 	/*
 	 * wait for all CPUs to sync up again, so that we don't continue
@@ -248,128 +751,21 @@ mtrrclock(void)				/* called from clock interrupt */
 	decref(&bar2);
 
 	dosync = 0;
-	splx(s);
-}
-
-static char*
-mtrr0(uvlong base, uvlong size, char *tstr)
-{
-	int i, vcnt, slot, type, mtype, mok;
-	vlong def, cap;
-	uvlong mp, msize;
-
-	if(!(m->cpuiddx & Mtrr))
-		return "mtrrs not supported";
-	if(base & (BY2PG-1) || size & (BY2PG-1) || size == 0)
-		return "mtrr base or size not 4k aligned or zero size";
-	if(!ispow2(size))
-		return "mtrr size not power of 2";
-	if(base & (size - 1))
-		return "mtrr base not naturally aligned";
-
-	if((type = str2type(tstr)) == -1)
-		return "mtrr bad type";
-
-	rdmsr(MTRRCap, &cap);
-	rdmsr(MTRRDefaultType, &def);
-
-	switch(type){
-	default:
-		return "mtrr unknown type";
-	case Writecomb:
-		if(!(cap & Capwc))
-			return "mtrr type wc (write combining) unsupported";
-		/* fallthrough */
-	case Uncacheable:
-	case Writethru:
-	case Writeprot:
-	case Writeback:
-		break;
-	}
-
-	vcnt = mtrrgetall();
-
-	slot = -1;
-	for(i = 0; i < vcnt; i++){
-		mok = mtrrdec(&mtrreg[i], &mp, &msize, &mtype);
-		if(slot == -1 && !mok)
-			slot = i;	/* good, but look further for exact match */
-		if(mok && mp == base && msize == size){
-			slot = i;
-			break;
-		}
-	}
-	if(slot == -1)
-		return "no free mtrr slots";
-
-	mtrrenc(&mtrreg[slot], base, size, type, 1);
-
-	coherence();
-
-	dosync = 1;
-	mtrrclock();
-
-	return nil;
-}
-
-char*
-mtrr(uvlong base, uvlong size, char *tstr)
-{
-	static QLock mtrrlk;
-	char *err;
-
-	qlock(&mtrrlk);
-	err = mtrr0(base, size, tstr);
-	qunlock(&mtrrlk);
-
-	return err;
-}
-
-int
-mtrrprint(char *buf, long bufsize)
-{
-	int i, n, vcnt, type;
-	uvlong base, size;
-	Mtrreg mtrr;
-	vlong def;
-
-	if(!(m->cpuiddx & Mtrr))
-		return 0;
-	rdmsr(MTRRDefaultType, &def);
-	n = snprint(buf, bufsize, "cache default %s\n",
-		type2str(def & Deftype));
-	vcnt = mtrrvcnt();
-	for(i = 0; i < vcnt; i++){
-		mtrrget(&mtrr, i);
-		if (mtrrdec(&mtrr, &base, &size, &type))
-			n += snprint(buf+n, bufsize-n,
-				"cache 0x%llux %llud %s\n",
-				base, size, type2str(type));
-	}
-	return n;
+	splx(x);
 }
 
+/* called from cpuidentify() */
 void
 mtrrsync(void)
 {
-	static vlong cap0, def0;
-	vlong cap, def;
+	State s;
 
-	rdmsr(MTRRCap, &cap);
-	rdmsr(MTRRDefaultType, &def);
-
-	if(m->machno == 0){
-		cap0 = cap;
-		def0 = def;
-		mtrrgetall();
+	if(getstate(&s) < 0)
+		return;
+	if(cpu0state.mask == 0){
+		cpu0state = s;
+		coherence();
 		return;
 	}
-
-	if(cap0 != cap)
-		print("mtrrcap%d: %lluX %lluX\n",
-			m->machno, cap0, cap);
-	if(def0 != def)
-		print("mtrrdef%d: %lluX %lluX\n",
-			m->machno, def0, def);
-	mtrrputall();
+	putstate(&cpu0state);
 }