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Roland Huisman
August 30th, 2012, 12:41 PM
This afternoon I've got an email if I was still interested
in an old Xerox computer having 8 inch drives. Well of course!
I'd have a wish to have once a real CP/M machine for a long while.

So I arranged a appointment for this evening to pick it up. Don't let him wait :D

And here it is. More than complete. A box full of new disks, the operating system,
Dbase, select word processor and their documentation.
I'd even got a Xerox printer with it. (wich is still in my car at the moment)

10083

He showed me the working (!) machine. But I do never trust those
mains filter caps. Cracked, so ready to explode and burn.
After I've replaced them I will turn on the machine again.

10084

I know there are also 5.25" drives for this computer. But does anyone
know if this machine supports 8" and 5.25" drives at the same time?

Regards, Roland

jharre
August 30th, 2012, 06:58 PM
Wow! Very cool. That's a nice looking setup.

All I have left from myX820 love affair is an etch 1 and an etch 2 motherboard. I tell myself that I'll build a floppy daughter board for the etch 2 one of these days (yeah, right).

I'm pretty sure you could use 8" OR 5 1/4" drives, but not at the same time. Is there a connector on the back of the drive enclosure to "daisy-chain" another box?

Chuck(G)
August 30th, 2012, 07:20 PM
Thanks to Al Kossow, there's a nice assortment of literature on the 820-II (http://bitsavers.informatik.uni-stuttgart.de/pdf/xerox/820-II/). I'd start with the Tech Ref.

(Yes, you can add a 5" floppy)

Roland Huisman
August 31st, 2012, 01:59 AM
@ jharre
Thanks for the compliments :) I will check for an extra connector in it.

@ Chuck
Wow, thank you for the link to this documentation.

I know the CP/M operating systems are machine specific.
But how about the programs such as games? Are they
also machine specific?

Chuck(G)
August 31st, 2012, 09:06 AM
I know the CP/M operating systems are machine specific. But how about the programs such as games? Are they
also machine specific?

It depends to a large extent on the nature of the game. Adventure (Colossal Cave) is a text-only game, so it will run on just about any CP/M system. Spacewar was originally written for TTY, so again, it's good.

But any game that uses graphics or unique terminal capabilities is going to be system-specific.

leeb
September 1st, 2012, 04:00 PM
SOOO VERY jelly!!!

... and Im luvin' the vintage computer in front of the vintage TV sitting next to the modern fridge! :p

:D

Roland Huisman
September 2nd, 2012, 05:08 AM
Hello leeb

Thank you! Old TV and radio is also my hobby.
In fact all the vintage electronics from the start.

Early radio, early TV, early VTR, early CD, early computing.... :D

Regards, Roland

(The TV is a Philips 21KX100A, K4 chassis)

enrico
March 13th, 2013, 02:58 PM
HI, would you able to send to me pic of your xerox controller, exact name and codes on its controller boards and the name of the big IC on it? Thanks Enrico

Roland Huisman
March 17th, 2013, 02:42 AM
HI, would you able to send to me pic of your xerox controller, exact name and codes on its controller boards and the name of the big IC on it? Thanks Enrico

You mean the FDD controller?

1229312294

Regards, Roland

enrico
March 17th, 2013, 10:05 AM
Thanks a lot, this the 1st time i can see how it made. I absolutely need it. I notever know how to search or to find it. Anybody have one to sell to me? Anybody can help me to find a bareboard with this kind of connector on which i could put and sold all those components? I found its schematic at the end of the document "Xerox 820 Service Manual" at this website http://www.classiccmp.org/dunfield/miscpm/x820serv.pdf Thanks for any suggestion or support.


1229312294

enrico
April 4th, 2013, 08:55 AM
Is there anybody who knows what is this old chip? And where to try to find it?
If it help what I know is that it used to do somenting like shift data register or Serial Shift Registers.
It has a TTL level signal on its pins, it has 14 pins. You can see it named U1 in the centre of this schematic: https://www.dropbox.com/s/zqhgar4g7ib5j4z/Xerox820_FDC_Schematic.pdf

Some pins are labelled on a schematics with:
1=D1, 2=D2, 3=D3, 4=D4,
10=A1, 11=A2, 12=A3, 13=A4, 14=A4,
15=ChipEnable (left to GND),
7=GND,
14=+5Vcc

Thanks

Steve Johnson
April 19th, 2013, 06:29 PM
Is there anybody who knows what is this old chip? And where to try to find it?
If it help what I know is that it used to do somenting like shift data register or Serial Shift Registers.
It has a TTL level signal on its pins, it has 14 pins. You can see it named U1 in the centre of this schematic: https://www.dropbox.com/s/zqhgar4g7ib5j4z/Xerox820_FDC_Schematic.pdf

Some pins are labelled on a schematics with:
1=D1, 2=D2, 3=D3, 4=D4,
10=A1, 11=A2, 12=A3, 13=A4, 14=A4,
15=ChipEnable (left to GND),
7=GND,
14=+5Vcc

Thanks

If it's for the 820, the 820 was based on the Ferguson Big Board. Documentation and parts lists for the Big Board are available here:
www.dtweed.com/docs (http://www.dtweed.com/docs/) Might give you a hint as to what it is.

enrico
April 20th, 2013, 03:11 AM
Thanks for you suggestions, the question has been solved.

Trying to rebuild the FDC card for my xerox 820-II motherboard, I have
discovered the presence of an IC named 733w01522 (U1) on the photo of the
original PCB which code I cannot read on the schematic not very readable
reported at the end of xerox820-II service manual. Sorry, I mistakenly
indicated a 14-pin TTL chips even though it was 16 pin.
Thanks for contribution of MIKES from the VCF he told me that the
733w01522 chip is a PROM and it is equivalent at 74S288 but also to others IC as
reported here http://www.hobbyroms.com/proms.html by Chuck.
U1 (74S288) and U2 (74S174) together constitute a "finite state machine" (so
they told to me cause I'm not so expert) whose purpose is to provide a read
clock and a read data to the chip WD1797 from raw data received from the
drive.
Then I need to discover the code that the chip could have recorded itself
(without having the original chip programmed with me!).
Upon the recommendation of Chuck Guzis I found the code listing on page 12
of the manual of the FDC1797's application notes. At this point, trusting to
this code I'd need to buy a programmed 74S288 (or equivalent).
There is another problem : a delay network U16=0447-0400-02
(https://www.dropbox.com/s/l4wxp3hdsf8s6wb/0447-0400-02.pdf )

After all those news, I was finally trying to figure out if it sould be better to
use of the schematic published on an old issue of Microcornucopia:
https://www.dropbox.com/s/4f8kblogrlzdr9m/FDC_from_Micro_Cornucopia_#22_Feb85.pdf (https://www.dropbox.com/s/4f8kblogrlzdr9m/FDC_from_Micro_Cornucopia_#22_Feb8)

Who wrote that so far article decided to build itself a FDC controller card for his
xerox 820-II extracting a block of its schematic from a Kaypro-II's
schematic really making very few changes and using a FDC WD1793 + WD9216 for
external separator data. Casually i have a socketed spare working kaypro-II motherboard
Due to its small number of components, and having already a WD1797 + WD921I'd just
and wiring that schematic it would be maybe more simple.
I'm waiting to receive a Vector plugboard 36+36 pin http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=200797705856 while I hope to be able to buy
a day a ready Xerox 820-II FDC board even I know that it's not very easy to find.
Thanks anyway for all the support that was given to me.
Regards
Enrico - Pisa (ITALY)