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Xerox 820-II - Set Up


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  Xerox 820-II - Set Up by Bill Degnan - 01/06/2011 10:22
The Xerox 820-II Computer with DD 8" and "Rigid" disk option.

Xerox is one of those computer companies, like Apple, whose computers you'd buy partially because of the brand name. At least that was the the case in early 80's. The initial reaction of consumers when the Xerox 820 series was announced was "Ah ha, watch out IBM, Xerox is getting in the game and they'll show everyone how to make a real computer".

It did not quite work out that way, the 820 series was pretty boring - no mouse and no hi-res graphics like the Lisa-inspiring Xerox Star, the production version of the Xerox Alto. Instead, the 820-II was a business machine, and as such it was only so-so when compared to the dozen or so business systems of the time. But at least you could say you had a Xerox. A CP/M Xerox. Yawn.


OK. It's 2011 and you have Xerox 820-II and you want to do something with it. Here's how you set it up:

1. Open the drive unit and make sure the hard drive is unlocked. There is a diagram on the drive to show you the unlocked position of the drive clamp. Use a screw driver to loosen the clamp and move it into the unlocked position, then re-tighten.

2. Attach the disk drive unit to the display unit. Note that if you don't have a 2nd drive, the secondary drive port is unused.

3. Power on the drive with no disk in the floppy drive. Let it run for at least 5 minutes. Don't leave the room, smell the drive for smoke if it has not been powered up for a long time. The chances that an unknown hard drive still works after years of not being used is not great.

4. Power on the Display. Ignoring the disk drive, the screen should show the system monitor program. The three menu options are L to load CP/M from disk; H to access the system monitor program; T to use the Xerox as a typewriter.

5. Insert the Xerox 820-II CP/M 2.2 disk in the floppy drive. The label should be facing to the right. Close the drive door so that it clicks.

6. Press L [return] to cause the computer attempt to boot the OS in the disk drive. The system will attempt to engage the CP/M disk and load CP/M into memory. L is short for "LA" - boot from drive A.

7. If you've made it this far, good. Now you're ready to set up the hard drive.

8. First check to see if the hard drive is already formatted, type

DIR G: [return] (or E: F: or H:). If a list of files appears, you already have a formatted disk, basically your done. Skip to the direction below for booting directly from the hard drive "rigid disk"

9. If CP/M tells you that there is no G drive (Select ERR...G:) you need to format the hard drive, or the drive controller electronics are bad, or the drive has deteriorated, etc....

FMT [return]

The Rigid Disk Initialization Utility for the Xerox 820-II. This utility partitions the hard drive into four logical drives, E, F,G,and H.

10. If the format is a success (wow) then it's time to load the OS into the G drive from the disk drive (A). G holds about 1Mb. E holds 4 Mb, F holds 2 Mb, and H 1Mb.

SYSGEN [return]

When prompted; the source drive is A. If successul the message "function complete" will appear.

When prompted; the destination drive is G. Follow the screen prompts to complete the transfer of the OS boot files to the hard drive partition G.

11. Next, copy the CP/M transient command files to the G drive.

PIP G:=A:*.*[V] [return]

([V] stands for verify the copy)

12. If that worked, you're done. Let's test it out. Power off the display unit, leaving the drive on, and remove the diskette from the floppy drive bay. Power the system back on. from the opening screen type

LG [return]

If everything is correctly set up and working the following message will appear on the screen when you first boot the system. Enter the "LG" command to boot from the OS stored in drive G. To boot from the floppy drive the command is "L" or "LA" (boot from A)

13. Important - After you boot from the hard drive, assuming it's drive G, CP/M re-assigns the logical drive names. Drive G becomes drive A, and the floppy drive becomes drive G.

Use the WHATSA command to see drive assignments

WHATSA If you boot from disk (and you just ran a DIR to E)

WHATSA If you boot from the hard disk after completing steps above

DIR A: - what's on the boot partition of the hard drive

DIR G: - what's on the diskette

Screen shot from a Star Trek text adventure. Games have been copied to the F partition.

More Pictures

  Xerox 820-II Schematics by William Dromgoole - 01/09/2011 11:16
Bil, I donated a complete book of schematics for the 820 to the MARCH library at the spring party in May 2009.

It is in a Xerox tan binder about 5 x 7 inches in size. The pages are small but readable. It was an original publication not a copy. It also had ROM listings and other technical info.


  Nice system by David Fenyes - 12/21/2011 11:51
Nice. The interesting thing about the Xerox 820 is that it is a slightly adapted Ferguson Big Board inside a Xerox case.

  Blew a Power Cap! by Bill Degnan - 06/23/2015 23:37
Took the system for a ride and blew a RIFA cap in the power supply of the disk drive...repairs to follow.



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