--- /sys/src/9k/k10/fns.h
+++ /sys/src/9k/k10/fns.h
@@ -196,7 +196,7 @@ extern void apictimerintr(Ureg*, void*);
 extern void apictprput(int);
 
 extern void ioapicinit(int, uintmem);
-extern void ioapicintrinit(int, int, int, int, u32int);
+extern void ioapicintrinit(int, int, int, int, int, u32int);
 extern void ioapiconline(void);
 
 /*
--- /sys/src/9k/k10/ioapic.c
+++ /sys/src/9k/k10/ioapic.c
@@ -12,6 +12,7 @@ typedef struct Rdt Rdt;
 
 struct Rbus {
 	Rbus	*next;
+	int	bustype;
 	int	devno;
 	Rdt	*rdt;
 };
@@ -90,7 +91,7 @@ rdtlookup(Apic *apic, int intin)
 }
 
 void
-ioapicintrinit(int busno, int apicno, int intin, int devno, u32int lo)
+ioapicintrinit(int bustype, int busno, int apicno, int intin, int devno, u32int lo)
 {
 	Rbus *rbus;
 	Rdt *rdt;
@@ -114,8 +115,12 @@ ioapicintrinit(int busno, int apicno, int intin, int devno, u32int lo)
 		rdt->lo = lo;
 	}else{
 		if(lo != rdt->lo){
-			print("multiple irq botch bus %d %d/%d/%d lo %.8ux vs %.8ux\n",
-				busno, apicno, intin, devno, lo, rdt->lo);
+			if(bustype == BusISA && intin < 16 && lo == (Im|IPhigh|TMedge)){
+				DBG("override: isa %d %.8ux\n", intin, rdt->lo);
+				return;	/* expected; default was overridden*/
+			}
+			print("multiple irq botch type %d bus %d %d/%d/%d lo %.8ux vs %.8ux\n",
+				bustype, busno, apicno, intin, devno, lo, rdt->lo);
 			return;
 		}
 		DBG("dup rdt %d %d %d %d %.8ux\n", busno, apicno, intin, devno, lo);
@@ -123,6 +128,7 @@ ioapicintrinit(int busno, int apicno, int intin, int devno, u32int lo)
 	rdt->ref++;
 	rbus = malloc(sizeof(*rbus));
 	rbus->rdt = rdt;
+	rbus->bustype = bustype;
 	rbus->devno = devno;
 	rbus->next = rdtbus[busno];
 	rdtbus[busno] = rbus;
@@ -281,7 +287,7 @@ ioapicintrenable(Vctl* v)
 	Rbus *rbus;
 	Rdt *rdt;
 	u32int hi, lo;
-	int busno, devno, vecno;
+	int bustype, busno, devno, vecno;
 
 	/*
 	 * Bridge between old and unspecified new scheme,
@@ -304,10 +310,11 @@ ioapicintrenable(Vctl* v)
 			if(mpisabusno == -1)
 				panic("no ISA bus allocated");
 			busno = mpisabusno;
-			devno = v->irq<<2;
+			devno = v->irq;
+			bustype = BusISA;
 		}
 	}
-	else if(BUSTYPE(v->tbdf) == BusPCI){
+	else if((bustype = BUSTYPE(v->tbdf)) == BusPCI){
 		/*
 		 * PCI.
 		 * Make a devno from BUSDNO(tbdf) and pcidev->intp.
@@ -330,7 +337,7 @@ ioapicintrenable(Vctl* v)
 
 	rdt = nil;
 	for(rbus = rdtbus[busno]; rbus != nil; rbus = rbus->next)
-		if(rbus->devno == devno){
+		if(rbus->devno == devno && rbus->bustype == bustype){
 			rdt = rbus->rdt;
 			break;
 		}
--- /sys/src/9k/k10/mp.c
+++ /sys/src/9k/k10/mp.c
@@ -4,6 +4,7 @@
 #include "dat.h"
 #include "fns.h"
 
+#include "io.h"
 #include "apic.h"
 
 /*
@@ -178,7 +179,7 @@ mpparse(PCMP* pcmp)
 {
 	u32int lo;
 	u8int *e, *p;
-	int devno, i, n;
+	int i, n, bustype;
 
 	p = pcmp->entries;
 	e = ((uchar*)pcmp)+l16get(pcmp->length);
@@ -274,10 +275,13 @@ mpparse(PCMP* pcmp)
 		 * May need to handle other buses here in the future
 		 * (but unlikely).
 		 */
-		devno = p[5];
-		if(memcmp(mpbus[p[4]]->type, "PCI   ", 6) != 0)
-			devno <<= 2;
-		ioapicintrinit(p[4], p[6], p[7], devno, lo);
+		bustype = -1;
+		if(memcmp(mpbus[p[4]]->type, "PCI   ", 6) == 0)
+			bustype = BusPCI;
+		else if(memcmp(mpbus[p[4]]->type, "ISA   ", 6) == 0)
+			bustype = BusISA;
+		if(bustype != -1)
+			ioapicintrinit(bustype, p[4], p[6], p[7], p[5], lo);
 
 		p += 8;
 		break;