diff --git a/Notes b/Notes
index 0399f5c..4e1703b 100644
--- a/Notes
+++ b/Notes
@@ -120,3 +120,4 @@ echo foo > bar should truncate bar
 make it work on one cpu
 make it work on a real machine
 release before acquire at end of sleep?
+check 2nd disk (i.e. if not in .bochsrc)
diff --git a/bio.c b/bio.c
index 251f2f9..49b52c9 100644
--- a/bio.c
+++ b/bio.c
@@ -75,9 +75,8 @@ bread(uint dev, uint sector)
   extern struct spinlock ide_lock;
 
   b = getblk(dev, sector);
-  if(b->flags & B_VALID){
+  if(b->flags & B_VALID)
     return b;
-  }
 
   acquire(&ide_lock);
   c = ide_start_rw(dev & 0xff, sector, b->data, 1, 1);
diff --git a/defs.h b/defs.h
index 1dd415c..752a7b7 100644
--- a/defs.h
+++ b/defs.h
@@ -116,6 +116,7 @@ void iinit(void);
 struct inode * iget(uint dev, uint inum);
 void ilock(struct inode *ip);
 void iunlock(struct inode *ip);
+void itrunc(struct inode *ip);
 void idecref(struct inode *ip);
 void iincref(struct inode *ip);
 void iput(struct inode *ip);
diff --git a/fs.c b/fs.c
index 80f522b..576bcb7 100644
--- a/fs.c
+++ b/fs.c
@@ -24,6 +24,9 @@ iinit(void)
   initlock(&inode_table_lock, "inode_table");
 }
 
+/*
+ * allocate a disk block
+ */
 static uint 
 balloc(uint dev) 
 {
@@ -52,7 +55,7 @@ balloc(uint dev)
     }
   }
   if (b >= size)
-    panic("balloc: out of blocks\n");
+    panic("balloc: out of blocks");
 
   bp->data[bi/8] |= 0x1 << (bi % 8);
   bwrite (bp, BBLOCK(b, ninodes));  // mark it allocated on disk
@@ -87,7 +90,11 @@ bfree(int dev, uint b)
   brelse(bp);
 }
 
-// returns an inode with busy set and incremented reference count.
+/* 
+ * fetch an inode, from the in-core table if it's already
+ * in use, otherwise read from the disk.
+ * returns an inode with busy set and incremented reference count.
+ */
 struct inode *
 iget(uint dev, uint inum)
 {
@@ -180,8 +187,9 @@ ialloc(uint dev, short type)
   }
  
   if (inum >= ninodes) 
-    panic ("ialloc: no inodes left\n");
+    panic ("ialloc: no inodes left");
 
+  memset(dip, 0, sizeof(*dip));
   dip->type = type;
   bwrite (bp, IBLOCK(inum));   // mark it allocated on the disk
   brelse(bp);
@@ -254,12 +262,11 @@ bmap(struct inode *ip, uint bn)
 }
 
 void 
-iunlink(struct inode *ip)
+itrunc(struct inode *ip)
 {
   int i, j;
   struct buf *inbp;
 
-  // free inode, its blocks, and remove dir entry
   for (i = 0; i < NADDRS; i++) {
     if (ip->addrs[i] != 0) {
       if (i == INDIRECT) {
@@ -278,10 +285,7 @@ iunlink(struct inode *ip)
     }
   }
   ip->size = 0;
-  ip->major = 0;
-  ip->minor = 0;
   iupdate(ip);
-  ifree(ip);  // is this the right order?
 }
 
 // caller is releasing a reference to this inode.
@@ -292,8 +296,10 @@ iput(struct inode *ip)
   if(ip->count < 1 || ip->busy != 1)
     panic("iput");
 
-  if ((ip->count == 1) && (ip->nlink == 0)) 
-    iunlink(ip);
+  if ((ip->count == 1) && (ip->nlink == 0)) {
+    itrunc(ip);
+    ifree(ip);
+  }
 
   acquire(&inode_table_lock);
 
@@ -425,7 +431,7 @@ writei(struct inode *ip, char *addr, uint off, uint n)
     }
     return r;
   } else {
-    panic ("writei: unknown type\n");
+    panic ("writei: unknown type");
     return 0;
   }
 }
@@ -451,10 +457,6 @@ namei(char *path, int mode, uint *ret_off, char **ret_last, struct inode **ret_i
   int i, atend;
   unsigned ninum;
 
-  if(mode == NAMEI_DELETE && ret_off == 0)
-    panic("namei no ret_off");
-  if(mode == NAMEI_CREATE && ret_last == 0)
-    panic("namei no ret_last");
   if(ret_off)
     *ret_off = 0xffffffff;
   if(ret_last)
@@ -550,9 +552,6 @@ wdir(struct inode *dp, char *name, uint ino)
   struct dirent de;
   int i;
 
-  if(name[0] == '\0')
-    panic("wdir no name");
-
   for(off = 0; off < dp->size; off += sizeof(de)){
     if(readi(dp, (char *) &de, off, sizeof(de)) != sizeof(de))
       panic("wdir read");
@@ -561,11 +560,8 @@ wdir(struct inode *dp, char *name, uint ino)
   }
 
   de.inum = ino;
-  for(i = 0; i < DIRSIZ && name[i]; i++){
-    if(name[i] == '/')
-      panic("wdir /");
+  for(i = 0; i < DIRSIZ && name[i]; i++)
     de.name[i] = name[i];
-  }
   for( ; i < DIRSIZ; i++)
     de.name[i] = '\0';
 
@@ -595,10 +591,8 @@ mknod1(struct inode *dp, char *name, short type, short major, short minor)
   struct inode *ip;
 
   ip = ialloc(dp->dev, type);
-  if (ip == 0) {
-    iput(dp);
+  if (ip == 0) 
     return 0;
-  }
   ip->major = major;
   ip->minor = minor;
   ip->size = 0;
diff --git a/ide.c b/ide.c
index 331553f..b999786 100644
--- a/ide.c
+++ b/ide.c
@@ -1,7 +1,5 @@
 /*
- * Minimal PIO-based (non-interrupt-driven) IDE driver code.
- * For information about what all this IDE/ATA magic means,
- * see the materials available on the class references page.
+ * Simple PIO-based (non-DMA) IDE driver code.
  */
 
 #include "types.h"
@@ -27,9 +25,11 @@ struct ide_request {
 struct ide_request request[NREQUEST];
 int head, tail;
 struct spinlock ide_lock;
-
+int disk_1_present;
 int disk_channel;
 
+int ide_probe_disk1(void);
+
 static int
 ide_wait_ready(int check_error)
 {
@@ -47,11 +47,9 @@ void
 ide_init(void)
 {
   initlock(&ide_lock, "ide");
-  if (ncpu < 2) {
-    panic ("ide_init: disk interrupt is going to the second  cpu\n");
-  }
-  ioapic_enable (IRQ_IDE, 1);
+  ioapic_enable (IRQ_IDE, ncpu - 1);
   ide_wait_ready(0);
+  disk_1_present = ide_probe_disk1();
 }
 
 void
@@ -80,7 +78,6 @@ ide_probe_disk1(void)
   // switch back to Device 0
   outb(0x1F6, 0xE0 | (0<<4));
 
-  cprintf("Device 1 presence: %d\n", (x < 1000));
   return (x < 1000);
 }
 
@@ -111,11 +108,8 @@ ide_start_rw(int diskno, uint secno, void *addr, uint nsecs, int read)
 {
   struct ide_request *r;
 
-  if(!holding(&ide_lock))
-    panic("ide_start_read: not holding ide_lock");
-
-  if(nsecs > 1)
-    panic("ide_start_read: nsecs too large");
+  if(diskno && !disk_1_present)
+    panic("ide disk 1 not present");
 
   while ((head + 1) % NREQUEST == tail)
     sleep (&disk_channel, &ide_lock);
@@ -140,12 +134,6 @@ ide_finish(void *c)
   int r;
   struct ide_request *req = (struct ide_request *) c;
 
-  if(c != &request[tail])
-    panic("ide_finish_read");
-
-  if(!holding(&ide_lock))
-    panic("ide_start_read: not holding ide_lock");
-
   if (req->read) {
     if ((r = ide_wait_ready(1)) >= 0)
       insl(0x1F0, req->addr, 512/4);
diff --git a/kalloc.c b/kalloc.c
index 989e3e8..cb79130 100644
--- a/kalloc.c
+++ b/kalloc.c
@@ -23,8 +23,6 @@ struct run {
 };
 struct run *freelist;
 
-void ktest(void);
-
 /*
  * initialize free list of physical pages. this code
  * cheats by just considering the one megabyte of pages
@@ -43,7 +41,6 @@ kinit(void)
   mem = 256; // XXX
   cprintf("mem = %d\n", mem * PAGE);
   kfree(start, mem * PAGE);
-  ktest();
 }
 
 void
@@ -130,46 +127,6 @@ kalloc(int n)
     rr = &(*rr)->next;
   }
   release(&kalloc_lock);
+  cprintf("kalloc: out of memory\n");
   return 0;
 }
-
-void
-ktest(void)
-{
-  char *p1, *p2, *p3;
-
-  // test coalescing
-  p1 = kalloc(4 * PAGE);
-  kfree(p1 + 3*PAGE, PAGE);
-  kfree(p1 + 2*PAGE, PAGE);
-  kfree(p1, PAGE);
-  kfree(p1 + PAGE, PAGE);
-  p2 = kalloc(4 * PAGE);
-  if(p2 != p1)
-    panic("ktest");
-  kfree(p2, 4 * PAGE);
-
-  // test finding first run that fits
-  p1 = kalloc(1 * PAGE);
-  p2 = kalloc(1 * PAGE);
-  kfree(p1, PAGE);
-  p3 = kalloc(2 * PAGE);
-  kfree(p2, PAGE);
-  kfree(p3, 2 * PAGE);
-
-  // test running out of memory
-  p1 = 0;
-  while((p2 = kalloc(PAGE)) != 0){
-    *(char**)p2 = p1;
-    p1 = p2;
-  }
-  while(p1){
-    p2 = *(char **)p1;
-    kfree(p1, PAGE);
-    p1 = p2;
-  }
-  p1 = kalloc(PAGE * 20);
-  if(p1 == 0)
-    panic("ktest2");
-  kfree(p1, PAGE * 20);
-}
diff --git a/proc.c b/proc.c
index 401188e..80141db 100644
--- a/proc.c
+++ b/proc.c
@@ -113,7 +113,7 @@ copyproc(struct proc* p)
 
   // Copy trapframe registers from parent.
   np->tf = (struct trapframe*)(np->kstack + KSTACKSIZE) - 1;
-  *np->tf = *p->tf;
+  memmove(np->tf, p->tf, sizeof(*np->tf));
   
   // Clear %eax so that fork system call returns 0 in child.
   np->tf->eax = 0;
diff --git a/string.c b/string.c
index 98253ed..10ea805 100644
--- a/string.c
+++ b/string.c
@@ -57,21 +57,3 @@ strncmp(const char *p, const char *q, uint n)
 	else
 		return (int) ((uchar) *p - (uchar) *q);
 }
-
-// Memcpy is deprecated and should NOT be called.
-// Use memmove instead, which has defined semantics
-// when the two memory ranges overlap.
-// Memcpy is here only because gcc compiles some
-// structure assignments into calls to memcpy.
-void *
-memcpy(void *dst, void *src, uint n)
-{
-  char *d = (char *) dst;
-  char *s = (char *) src;
-
-  while(n-- > 0)
-    *d++ = *s++;
-
-  return dst;
-}
-
diff --git a/syscall.c b/syscall.c
index 2918bb0..2d08a0e 100644
--- a/syscall.c
+++ b/syscall.c
@@ -21,8 +21,6 @@
  * Arguments on the stack, from the user call to the C
  * library system call function. The saved user %esp points
  * to a saved program counter, and then the first argument.
- *
- * Return value? Error indication? Errno?
  */
 
 /*
@@ -51,7 +49,6 @@ fetchbyte(struct proc *p, uint addr, char* c)
   return 0;
 }
 
-// This arg is void* so that both int* and uint* can be passed.
 int
 fetcharg(int argno, void *ip)
 {
@@ -366,9 +363,6 @@ sys_chdir(void)
   if((l = checkstring(arg0)) < 0)
     return -1;
 
-  if(l >= DIRSIZ)
-    return -1;
-
   if ((ip = namei(cp->mem + arg0, NAMEI_LOOKUP, 0, 0, 0)) == 0)
     return -1;
 
@@ -436,11 +430,8 @@ sys_dup(void)
     return -1;
   if(cp->fds[fd] == 0) 
     return -1;
-  if (cp->fds[fd]->type != FD_PIPE && cp->fds[fd]->type != FD_FILE)
+  if ((ufd1 = fd_ualloc()) < 0) 
     return -1;
-  if ((ufd1 = fd_ualloc()) < 0) {
-    return -1;
-  }
   cp->fds[ufd1] = cp->fds[fd];
   fd_incref(cp->fds[ufd1]);
   return ufd1;
diff --git a/vectors.pl b/vectors.pl
index 368aad7..33cde90 100755
--- a/vectors.pl
+++ b/vectors.pl
@@ -2,8 +2,8 @@
 
 # Generate vectors.S, the trap/interrupt entry points.
 # There has to be one entry point per interrupt number
-# since otherwise there's no way to tell the interrupt
-# number.
+# since otherwise there's no way for trap() to discover
+# the interrupt number.
 
 print "/* generated by vectors.pl */\n";
 print "/* handlers */\n";