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X > XEROX  > 8 / 16   

8 / 16

The "best of both worlds". The Xerox 8 / 16 belongs to a family which appeared at the end of the 8 bit era, when MS-DOS began to be a standard for the 16-bit systems. It has two CPUs, the Z80 allows the use of CP/M and the 8086 is for MS DOS and CP/M 86. This computer was actually two computers sharing certain resources, like the display, the power supply and the floppies but essentially seperate.
This computer was one of the first, if not the first PC-sized computer that had concurrent processing (not time share, but real honest to goodness concurrent processing). One could start a task on either operating system, say a spread sheet, and then hot key over to the other processor and perform another task, all while the other "side" was working at full speed at it's task. Because the 16/8 was actually two computers in one, both sides worked at full capacity and did not share ram or other system resources required for processing data: they worked at full speed regardless of whether or not the other side was in use. Only the "active side" had access to the video, floppies and the hard drive (if avaialble), but with dual floppies, one floppy could be assigned for the 8 bit side and one for the 16 bit side. In that instance, each side would access the its assigned floppy when brought to the active side.

The 16/8 is made of four units :
- a 12'' monochrom monitor, housing the whole hardware of the system, like in the Apple Macintosh,
- the keyboard, very complete,
- the disks (two 5''1/4 disks, a hard-disk (5 MB, later 10 MB) was optional),
- an expansion box meant to house the different expansion boards.

There was also a Diablo printer in option. The whole system thus took quite some room on your desktop!

After the presentation of the first 16/8 in 1983, Xerox launched a new version in 1984, faster, more compact and sold with a hard-disk.

Unfortunately the 16/8 was a bit obsolete as the 8-bit professional systems were dying slowly and the 16/8 wasn't offering much more than an IBM PC launched a few years before. The price of the system wasn't even attractive.
Xerox stopped the production of all its micro-computers at the start of the year 1985.

This computer is the direct successor of the Xerox 820 series, which could be almost converted into a Xerox 8/16 with a special 8086 board.

Dale Carpenter adds:
Several things, an 820-II has an extra expansion slot on the motherboard. if you put the 16-bit card into that slot your 820-II is now a 16/8.
Your picture shows a rectangular box called an EM-II (expansion module - II) to add it to a 16/8 you remove the 16-bit card and install it in the card cage in the center of the EM-II then install the card with 2 wide ribbon cables attached(coming from the EM-II) into the expansion slot on the motherboard.
The EM-II has either 1 hard drive, 1 floppy or 1 of each. The system supported the external drives also, the dual 5.25" and 8" boxes.
One final note not mentioned: all of the 8" drive boxes had an expansion plug on the back you could daisey chain up to 4 drive units onto any of the 820, 820-II and 16/8 machines.


Thanks to chrism3667 for the picture

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I am looking for one of these at a cheap price, I will pay up to 100$ including shipping if I have to pay for it
Email is

Tuesday 22nd September 2020
Jay (Washington State USA)

As a working technology journalist I got a 16/8 to test and then write about. The ability to be able to swap between MSDOS and CP/M at will was great. It as an elegant system and came with a cool Xerox printer. I gave it an OK review but argued that people would use either CP/M or MSDOS but not both. The nice people at Xerox never asked for it back so I wrote all my copy on it for the next four years - lucky me!

Sunday 17th November 2019
Colin Barker (United Kingdom)

Worked for Balcones Computer Corporation with Robert Burns (the MicroManiac) and brother Jay Bell.
Balcones Consulted for Xerox and took the Xerox 820 from I to Xerox 820-II. If you look through the BIOS code documentation you''ll see references to Balcones. Balcones drove adding the expansion connector and developed the 16/8 CPU card for Xerox. The expansion chassis used a WD1002 controller to interface the external floppy and hard disk (same type of controller used in the Kaypro 10)...both Kaypro and Xerox 820 were derived from the "Big Board". Our first prototypes of the 16/8 CPU card was created using a "multiwire" connection method, but production versions were multilayer printed circuit boards. I still have at least one of the multiwire prototypes. Jay Bell always said that the weak link in the 8086 card design was the use of many PAL chips whose timing did not always meet spec and thus created an instability sometimes.
Balcones also sold their Accounting System (The Boss System) which was sold by Xerox and Rank Xerox worldwide. A lawsuit relating to Xerox royalties for various projects ended up taking Balcones down. Many of Balcones employees transitioned to PC''s Ltd (later called Dell) where Jay Bell and Robert Burns designed the first 286 system for PC''s Ltd which was Michael Dell''s first in house Computer design.

Sunday 23rd July 2017
James Bell (Austin, Texas)


NAME  8 / 16
TYPE  Professional Computer
YEAR  1983
KEYBOARD  Full-stroke keyboard with numeric and editing keypads, arrow keys, 12 function keys
CPU  Zilog Z80A @ 4 Mhz (8-bit)
8086 @ 4,77 Mhz (16-bit)
SPEED  4 Mhz (Z80A) and 4,77 Mhz (8086)
RAM  64 KB (Z80) + 128 KB (8086)
ROM  4 KB Bootstrap
TEXT MODES  80 x 25 / 40 x 25
GRAPHIC MODES  640 x 256
COLORS  Unknown
SOUND  Beeper
I/O PORTS  Serial 9600 bauds, Internal Expansion Slot, External Floppy Connector
BUILT IN MEDIA  One or Two 5.25'' or 8'' disk-drives
OS  CP/M (8bit), CP/M 86 (16bit, MSDOS optional)
PERIPHERALS  Memory expansion, Graphical board, printer, hard-disk, mouse
PRICE  from 4575 to 8390 (France, 1984)

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