ftp://ftp.fnet.fr/pub/system/linux/Mips/misc/magnum-4000/

is where the floppies are.  You may wish to review the following from
the Linux/mips faq.  Don't know if it would be helpful, or if it is
accurate about the serial console.

Warner


Mips Magnum 4000 / Olivetti M700-10

These two machines are almost completely identical. Back during the
ACE initiative Olivetti licensed the Jazz design and marketed the
machine with Windows NT as OS. MIPS Computer Systems, Inc. itself
bought the Jazz design and marketed it as the MIPS Magnum 4000 series
of machines. Magnum 4000 systems were marketed with Windows NT and
RISC/os as operating systems.

The firmware on the machine depended on the operating system which was
installed. Linux/MIPS supports only the little endian firmware on
these two types of machines. Since the M700-10 was only marketed as an
NT machine all M700-10 machines have this firmware installed. The MIPS
Magnum case is somewhat more complex. If your machine has been
configured big endian for RISC/os then you need to reload the little
endian firmware. This firmware was originally included on a floppy
with the delivery of every Magnum. If you don't have the floppy
anymore you can download it via anonymous ftp from ftp://ftp.fnet.fr.

It is possible to reconfigure the M700 for headless operation by
setting the firmware environment variables ConsoleIn and ConsoleOut to
multi()serial(0)term(). Also try the command listdev which will show
the available ARC devices.

In some cases, like where the G364 graphics card is missing but the
console is still configured to use normal graphics it will be
necessary to set the configuration jumper JP2 on the board. After the
next reset the machine will reboot with the console on COM2.