diff --git a/boot.py b/boot.py
index 726da58..a42b53f 100644
--- a/boot.py
+++ b/boot.py
@@ -1,6 +1,27 @@
+import time
+from machine import PDP1170
+from kw11 import KW11
+from kl11 import KL11
+from rp import RPRM
 
-def boot_hp(p, /, *, addr=0o10000):
-    """Read the first 1KB of drive 0 into location 'addr'."""
+
+def boot_hp(p, /, *, addr=0o10000, deposit_only=False):
+    """Deposit, then run, instructions to read first 1KB of drive 0 --> addr.
+    RETURN VALUE:  addr if deposit_only else None
+
+    If no 'addr' given, it defaults to something out of the way.
+
+    If not deposit_only (default):
+       * The instructions are loaded to 'addr'
+       * They are executed.
+       * Return value is None.
+       * NOTE: The next start address depends on what those instructions do.
+       *       TYPICALLY, the next start address will be zero.
+
+    If deposit_only:
+       * The instructions are loaded to 'addr'
+       * 'addr' is returned.
+    """
 
     # this is the sort of thing that would be keyed in from
     # the console switches (if the machine was not equipped
@@ -29,12 +50,33 @@ def boot_hp(p, /, *, addr=0o10000):
     for o, w in enumerate(program_insts):
         p.physRW(addr + o + o, w)
 
-    return addr
+    p.r[p.PC] = addr
+    if not deposit_only:
+        p.run()
+
+        # at this point in real life the user would have to set the switches
+        # to deposit zero into the PC and then hit start; that takes time
+        # and means the bootstrap doesn't have to have code to wait for the
+        # drive to complete the read operation. Instead of adding code to
+        # the "pretend this was keyed in" program above, this delay works.
+        time.sleep(0.25)
+
+    return addr if deposit_only else None
 
 
-def boot_file(p, fname, /, *, addr=0, little_endian=True, skipwords=8):
-    """Read a raw binary image of pdp11 data into location 'addr'."""
+def boot_bin(p, fname, /, *, addr=0, deposit_only=False,
+             little_endian=True, skipwords=8):
+    """Read a binary file 'fname' into location 'addr' and execute it.
+    RETURN VALUE:  addr if deposit_only else None
 
+    NOTE: fname is in the host system, not on an emulated drive.
+    If no 'addr' given, it defaults to ZERO.
+    If deposit_only=True, the instructions are not executed.
+
+    little_endian (default True) dictates the fname byte order.
+    skipwords (default 8 -- a.out header) will seek that many 16-bit
+    words into the file before beginning to load.
+    """
     with open(fname, 'rb') as f:
         bb = f.read()
 
@@ -65,20 +107,50 @@ def boot_file(p, fname, /, *, addr=0, little_endian=True, skipwords=8):
 
         for a, w in enumerate(words[skipwords:]):
             p.physmem[a] = w
-    return p
 
+    p.r[p.PC] = addr
+    if not deposit_only:
+        p.run()
+    return addr if deposit_only else None
+
+
+def boot_unix(p=None, loglevel='INFO'):
+
+    if p is None:
+        p = PDP1170(loglevel='INFO')
+
+        p.associate_device(KW11(p.ub), 'KW')    # line clock
+        p.associate_device(KL11(p.ub), 'KL')    # console
+        p.associate_device(RPRM(p.ub), 'RP')    # disk drive
+
+        # load, and execute, the key-in bootstrap
+        boot_hp(p)
+
+    print("Starting PDP11; this window is NOT THE EMULATED PDP-11 CONSOLE.")
+    print("*** In another window, telnet/nc to localhost:1170 to connect.")
+    print("    Terminal should be in raw mode. On a mac, this is a good way:")
+    print("         (stty raw; nc localhost 1170; stty sane)")
+    print("")
+    print("There will be no prompt; type 'boot' in your OTHER window")
+    print("")
+    print("Then, at the ':' prompt, typically type: hp(0,0)unix")
+
+    p.run(pc=0)
+
+
+# USE:
+#    python3 boot.py
+#
+# to start up unix (or whatever system is on the drive)
 
 if __name__ == "__main__":
-    import time
-    from machine import PDP1170
-    p = PDP1170(loglevel='INFO')
-    pc = boot_hp(p)
-    print("starting PDP11; telnet/nc to localhost:1170 to connect to console")
-    print("There will be no prompt; type 'boot' to start boot program")
-    p.run(pc=pc)
-    # technically need to confirm the drive is RDY, i.e., the read
-    # completed, but using a delay is a lot simpler and works fine.
-    # In real life, humans would have manipulated console switches to
-    # start execution at location 0, which is also a source of delay. :)
-    time.sleep(0.05)
-    p.run(pc=0)
+    import argparse
+
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--debug', action='store_true')
+    args = parser.parse_args()
+
+    if args.debug:
+        boot_unix(loglevel='DEBUG')
+    else:
+        boot_unix()