Date   : Mon, 20 Jul 1992 06:24:48 PDT
From   : Sprague.Wbst311@xerox.com
Subject: Re: Xerox 16/8??

Get in touch with me (EMail or phone), and I'll see if we can get you some
documentation for your computer.

The Xerox 16/8 is nothing more than a Xerox 820-II with an 8086 single boad
computer (the 16/8 card) plugged into the expansion slot.  Both are
independent, with their own ROM, RAM, etc, but they share the drives and
console.

The system boots up in stnadard CP/M, and by running a few commands, can switch
into concurrent CP/M-80 / CP/M-86 mode.  It also ran vanella MS-DOS (not
PC-DOS), but this (IMOHO) is useless on the 8" drive machine, and is of
questionable value on the 5.25" 16/8 DEM since most MS-DOS programs are written
for PC-DOS.  For that matter, I don't think CP/M-86 is of much use either, due
to the lack of available software.

> I am looking for any info about the hardware, schematics etc.  I am also
> looking for info on video mode programming (escape codes etc.).

Drop me a line.  I'll see about getting you a copy of the documentation.

> Is it Xerox 820 compatible?

Yes, in CP/M mode, but it's somewhat better than the old 820.  The 820-II and
16/8 support double density disks .... something you don't get on the old 820
without a spcial harware upgrade.

> It tells me I have 60K bios, but how much memory is there really?

On the motherboard (containing the Z80), there is 64K of RAM (not BIOS), 60K of
which is available for CP/M.  The 16/8 board usualy contains 128K of RAM, but
would be 256K if it has the RAM expansion board.  This RAM is available to
CP/M-86 and/or MS-DOS.

> Does anyone know if I can get the 8" single sided diskettes?

Check out computer flea markets and the like.  I think I might have some, but I
am not sure.

> Is it possible to expand the disk storage?  Double sided? 5-1/4"?

I am going to answer this for all three of the Xerox machines, since the 16/8
can be used as an 820-II.  Also note that a single sided 8" floppy holds more
data than a double sided 5.25" one.  A double sided 8" floppy on the Xerox
820-II or 16/8 held almost 1 Meg.

The Xerox 820 supported two 8" or 5.25" drives.  Single density, but the disks
could be single of double sided.  (Some with older BIOS supported three drives,
but they were only single sided).   5.25" disks were next to useless due to
limited storage.

The Xerox 820-II supported two 8" or 5.25" drives.  Single or double density
and single or double density.

The 16/8 could support two 8" or two 5.25" disks.  It's not quite as simple as
that though.  CP/M-86 and MS-DOS on the 16/8 would ONLY support the 5.25" DEM
(Disk Expansion module), and would NOT boot on the normal 5.25" drives, though
820-II disks would.  Note that to install the DEM, the Disk controller would be
removed (as there was already a Western Digital Hard/Floppy controller in the
DEM), and a buffer board would be added in the 820's expansion slot.  The 16/8
board was installed in a card cage in the DEM.

There is one pin on the Disk interface (on a non 16/8 DEM machine) that
determines if 8" or 5.25" disks are installed.  If I remember right, it's pin
2, and if grounded, it means that 5.25" disks are installed.  In all cases
(except the early 820's) the Xerox machine ONLY supports two floppies.

Last, while it is not simple, I have converted an 820-II to use 5.25" High
Density disk drives.  As far as the 820-II is concerned, it has 8" drives
installed, and treates them as such.  The tricky part is what to do with Drive
Ready.

> How do I program serial output baud rates, etc.?

There is a program on the Boot disk called CONFIGUR.  It is used to set up the
serial ports, the floppy step rate, keyboard interface (7 or 8 bits) and a few
other things.

> It is a Xerox (diablo) daisy wheel printer.  anyone know about it?
> It said, on the plate by the dip switch, something about having a
> "Special baud rate"  it also has 300 and 1200.

I don't know about a special baud rate, but the 820-II has no trouble with a
printer up to 9600 baud (I have never taken it any further).  Some of the 820's
documentation talks about the printer.

                               ~ Mike  (sprague.wbst311@xerox.com)

Work Phone:  (716) 422-0472
Home Phone:  (315) 986-9863