diff --git a/gnu/dist/gdb6/gdb/i386nbsd-nat.c b/gnu/dist/gdb6/gdb/i386nbsd-nat.c
index c7f40dad2a54..f89f82df1440 100644
--- a/gnu/dist/gdb6/gdb/i386nbsd-nat.c
+++ b/gnu/dist/gdb6/gdb/i386nbsd-nat.c
@@ -44,22 +44,22 @@ i386nbsd_supply_pcb (struct regcache *regcache, struct pcb *pcb)
   /* The following is true for NetBSD 1.6.2 and after:
 
      The pcb contains %esp and %ebp at the point of the context switch
-     in cpu_switch().  At that point we have a stack frame as
-     described by `struct switchframe', which for NetBSD has the
-     following layout:
+     in cpu_switch()/cpu_switchto().  At that point we have a stack frame as
+     described by `struct switchframe', which for NetBSD (2.0 and later) has
+     the following layout:
 
-     interrupt level
      %edi
      %esi
      %ebx
      return address
 
      we reconstruct the register state as it would look when we just
-     returned from cpu_switch().
+     returned from cpu_switch()/cpu_switchto().
 
-     For core dumps the pcb is saved by savectx() and contains the
-     stack pointer and frame pointer.  In this case extract a return
-     address from the stack.  */
+     For core dumps the pcb is saved by savectx()/dumpsys() and contains the
+     stack pointer and frame pointer.  A new dumpsys() fakes a switchframe
+     whereas older code isn't reliable so use an iffy heuristic to detect this
+     and use the frame pointer to recover enough state.  */
 
   /* The stack pointer shouldn't be zero.  */
   if (pcb->pcb_esp == 0)
@@ -69,7 +69,8 @@ i386nbsd_supply_pcb (struct regcache *regcache, struct pcb *pcb)
 
   if ( (unsigned long)sf.sf_eip >= (unsigned long)0xc0100000 )
     {
-      /* Yes, we have a frame that matches cpu_switch().  */
+      /* Yes, we have a switchframe that matches cpu_switchto() or
+         the new dumpsys().  */
 
       pcb->pcb_esp += sizeof (struct switchframe);
       regcache_raw_supply (regcache, I386_EDI_REGNUM, &sf.sf_edi);
@@ -83,8 +84,8 @@ i386nbsd_supply_pcb (struct regcache *regcache, struct pcb *pcb)
     {
       CORE_ADDR pc, fp;
 
-      /* No, the pcb must have been last updated by savectx() in
-         dumpsys. Use the frame pointer to recover enough state.  */
+      /* No, the pcb must have been last updated by savectx() in old
+         dumpsys(). Use the frame pointer to recover enough state.  */
 
       read_memory (pcb->pcb_ebp, (gdb_byte *) &fp, sizeof(fp));
       read_memory (pcb->pcb_ebp + 4, (gdb_byte *) &pc, sizeof(pc));