diff --git a/bootother.S b/bootother.S
index eee5ebe..8f2b2ce 100644
--- a/bootother.S
+++ b/bootother.S
@@ -14,7 +14,7 @@
  * mp.c puts the correct %esp in start-4, and the place to jump
  * to in start-8.
  *	
- * Credit: Cliff Frey
+ * Credit: Cliff Frey and Plan 9
  */
 
 .set PROT_MODE_CSEG,0x8		# code segment selector
diff --git a/mp.c b/mp.c
index d4284dc..f267b8a 100644
--- a/mp.c
+++ b/mp.c
@@ -91,20 +91,18 @@ enum {					/* LAPIC_TDCR */
 };
 
 #define APBOOTCODE 0x7000 // XXX hack
+#define MPSTACK 512
 
-static struct MP* mp;  /* The MP floating point structure */
+static struct MP* mp;  // The MP floating point structure
 static uint32_t *lapicaddr;
 static struct cpu {
-  uint8_t apicid;       /* Local APIC ID */
-  int lintr[2];		/* Local APIC */
+  uint8_t apicid;       // Local APIC ID
+  int lintr[2];		// Local APIC
+  char mpstack[MPSTACK]; // per-cpu start-up stack, only used to get into main()
 } cpus[NCPU];
 static int ncpu;
 static struct cpu *bcpu;
 
-// per-cpu start-up stack, only used to get into main()
-#define MPSTACK 512
-char mpstacks[NCPU * MPSTACK];
-
 static int
 lapic_read(int r)
 {
@@ -361,7 +359,7 @@ mp_init()
     if (cpus+c == bcpu) continue;
     cprintf ("starting processor %d\n", c);
     release_grant_spinlock(&kernel_lock, c);
-    *(unsigned *)(APBOOTCODE-4) = (unsigned) mpstacks + (c + 1) * MPSTACK; // tell it what to use for %esp
+    *(unsigned *)(APBOOTCODE-4) = (unsigned) (cpus[c].mpstack) + MPSTACK; // tell it what to use for %esp
     *(unsigned *)(APBOOTCODE-8) = (unsigned)&main; // tell it where to jump to
     lapic_startap(cpus + c, (uint32_t) APBOOTCODE);
     acquire_spinlock(&kernel_lock);