========================================================================
                              RFC 473
========================================================================

Network Working Group                                          D. Walden
Request for Comments: 473                                        BBN-NET
NIC: 14811                                              28 February 1973


                             MIX and MIXAL?

   Is there an interpreter for Knuth's hypothetical computer, MIX,
   together with an assemble for the MIX assembly language, MIXAL,
   available on any ARPA Network Host? If not, will not some Network
   Host make them available (cheaply)?--it would be considerable service
   to all of us who are students of the "Art of Computer Programming."


========================================================================
                              RFC 485
========================================================================

Network Working Group                                    John R. Pickens
RFC # 485                                                UCSB
NIC # 15063                                              19 March 1973
References NWG/RFC #473


                         MIX and MIXAL at UCSB

The following, in response to David Walden's MIX query (RFC#473) was
written by a graduate student at UCSB.  Questions regarding "cheap"
usage should be directed to Roland F. Bryan (RFB) at UCSB.
-----------------------------------------------------------------------

Mark Scott Johnson
18 March 1973

    I wrote a MIXAL assembler and a MIX simulator last summer.  The
assembler is written in SNOBOL4 and, unfortunately, is fairly expensive
to run.  The assembler has been fairly well debugged and is documented.
However, although the MIX simulator is written (in 360 Assembler), it
has only been partially debugged.  Due to the resumption of school and
other commitments, I was unable to give the simulator a thorough
debugging.  All the simulated instructions except I/O instructions have
been tested somewhat and appear to be operating well.  Also, card reader
input and printer output are operational, but my simulation of disk
files and magnetic tape has not been completed.  There is presently no
documentation for the simulator.  Very little documentation is needed,
however, since the simulator follows almost to the letter the
specifications detailed in _Fundamental_Algorithms_.

    If anyone is interested in using the assembler and/or the simulator,
I will be happy to supply what documentation exists plus some
information on how the programs can be accessed.  Also, if anyone is
interested in the source code for the programs, I will be happy to send
it.  I hope to be able to finish the simulator this next quarter.  If
anyone wants to use the system and if they should find any bugs, I will
do my best to maintain and correct the programs.



========================================================================
                              RFC 494
========================================================================

Network Working Group                                          D. Walden
Request for Comments: 494                                        BBN-NET
NIC: 15359                                                 20 April 1973
References: RFCs 473, 485


               Availability of MIX and MIXAL in the Network

   In RFC 473 I requested information on the existence of assemblers and
   interpreters for Knuth's hypothetical MIX computer.  Following is a
   summary of the responses to my earlier RFC.

   First the rumors: (1) There is rumored to be a MIX interpreter
   available on the University of Utah PDP-10, but not assembler; and
   (2) There is rumored to be a MIX interpreter available on the SU-AI
   PDP-10.

      Now the facts:

   A fairly well debugged and documented MIXAL assembler exists for the
   UCSB 360/75.  A partially debugged MIX interpreter also exists.  See
   RFC 485 for additional information.

   Box MIX and MIXAL are available on the UCSD B6700; although,
   according to Ken Bowles, they are not currently being handled as
   fully supported products, and there may be some remaining bugs in the
   systems. However, MIX and MIXAL are available for network users, and
   Ken says they will be happy to receive notification of any errors
   found in the MIX and MIXAL and will attempt to get corrections made
   in due course. Contact Ken Bowles at UCSD for further information.

   MIX and an assembler for MIX are available for network use on the
   UCLA 360/91.  These systems have had considerable use, and they are
   documented.  Contact Bob Braden at CCN for further information.

   Finally: The Computer Science Center at Stanford University
   apparently has available a standard package for exporting the MIX
   systems to 360s and 370s.

