A BYTE SHORT TAKE: Portable Mainframe
 
How Portable Can a Portable Mainframe Be?
 
Microbytes Daily News Service
Copyright (c) 1989, McGraw-Hill, Inc.
How portable can a portable mainframe be? Pretty portable, it
turns out.
 
A few months ago, Opus Systems introduced its Personal Mainframe,
a coprocessor card designed around the Motorola 88000 RISC CPU;
the card can plug into a 16-bit slot in any AT clone. Now Opus is
back, this time with a faster version of the card and a lot more
software to run on it -- including Unix, X Windows, Motif, word
processors, and spreadsheets. Better still, Opus is offering the
card installed in a lunchbox-style portable computer, making it
the first portable RISC workstation. At 22 pounds, it's certainly
portable -- and at 21 MIPS, it can outrun many of its deskbound
workstation brethren.
 
The Portable Mainframe is actually a 16-MHz, 80386SX-based
lunchbox portable made by NEC -- a conventional AC-only portable
system with a 640- by 480-pixel monochrome gas plasma display,
2 megabytes of RAM, a 40-megabyte hard disk, and three expansion
slots. In one of those slots is the Opus coprocessor card -- it
has a Motorola 88000 running at either 20 or 25 MHz, from 4 to 24
megabytes of RAM, and twin 16K caches for instructions and data.
 
Once the 88000 is running Unix, the 80386SX handles all
I/O -- including screen updates, keyboard input, printer and
serial ports, and disk drives. That leaves the 88000 free to run
Unix, and it runs it faster than many other RISC workstations,
including SPARC-based Suns and MIPS-based DECstations. It even
benchmarks faster than Data General's AViiON, which uses the
same RISC CPU -- probably because so much of the Portable
Mainframe's I/O housekeeping is done by the SX. With a 20-MHz
88000, the Portable Mainframe is rated at 17 VAX MIPS; at
25 MHz, it's 21 MIPS. (For comparison, a 16-MHz 80386 offers
about 3 MIPS.)
 
While it's handling the 88000's I/O, the 80386SX has lots of
spare time free for running programs under DOS.  You can
simultaneously run Unix on the 88000 and DOS on the SX; you can
also transfer files between UNIX and DOS, "hot key" back and
forth between them, and even execute commands and programs of
either operating system from the other.
 
But the Portable Mainframe does have an Achilles' heel: the
creaky old 16-bit AT bus. Because the coprocessor card plugs into
an ordinary AT slot, it's easy to add other AT-compatible cards
to the system -- a big advantage. But the AT bus also slows down
I/O throughput. Although the 88000 CPU may be rocketing along at
21 MIPS, the AT bus is limited to a throughput of around 16
megabytes per second. That's just about enough to constantly
update a VGA screen -- but not nearly enough for the oversize
screens favored by most of today's workstation users for
engineering simulations. Unless Opus adds a video connector to
its coprocessor card -- or designs a Micro Channel or EISA
version of the card -- the Portable Mainframe may never be the
machine of choice for studying fluid dynamics or structural
stress.
 
On the other hand, it may turn out to be perfect for
recalculating spreadsheets -- a job that requires pure processor
power, not pretty pictures. Regular DOS spreadsheets such as
Lotus 1-2-3 will run on the Portable Mainframe, of course -- but
only at DOS speeds. However, Q-Calc, a Lotus-compatible Unix
spreadsheet program, has an 88000 version that should be
available by the time you read this. In addition, Lotus 1-2-3
will be available soon in a Unix port done using XDOS from
Hunter Systems. A Unix version of WordPerfect also runs on the
Portable Mainframe, and other 88000-based software is rapidly
becoming available thanks to the 88Open Consortium -- a group of
88000-based workstation vendors who've developed a standard
software environment so that the same shrink-wrapped software
can run on any 88Open-compatible computer.
 
Does the Portable Mainframe really qualify as a portable
mainframe? It may have mainframe MIPS; it certainly doesn't have
mainframe throughput, although it doesn't have a mainframe price,
either. And at just under 1 MIP per pound, it's certainly the
most concentrated processing kick available -- and with its
merger of DOS compatibility and RISC power, it may be just what
some PC users have been waiting for.
 
The Facts:
$13,995 (20-MHz version)
 
Opus Systems
20863 Stevens Creek, Building 400
Cupertino, CA 95014
(408) 446-2110
 
 
                              --- Frank Hayes
 
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