Data General NOVA 4/C help

Jay Jaeger cube1 at
Sun Oct 18 12:23:19 CDT 2015

On 10/17/2015 3:16 PM, Henk Gooijen wrote:
> I picked up the NOVA 4 last Thursday. I had help carrying all the stuff
> (disassembled) downstairs from the attic. At home I had to unload the van
> single-handed. Went well, although I felt my back that evening ...
> Today, I cleaned the rack, as all boxes were still on the floor. There
> was little dust, the machine was well taken care of.
> After the cleaning I mounted the hard disk drive on the slides. The hard
> drive is a model 6101-S2 (12.5 MB fixed disk). On the top plate of the
> hard disk is an 8" Qume floppy disk drive mounted. The hard disk and
> the floppy disk form one unit, never seen this construction before!
> The colored twisted-pair flatcable from the floppy drive goes to the
> hard disk and another colored twisted-pair flat cable goes to the
> NOVA 4/C computer, connecting on a paddle board using an edge connector.

My Nova 4 and Eclipse S/140 have a 6100 DG winchester hard disk with the
floppy on a hinge sitting over the hard disk, as a single unit.  I think
it is the same family as yours (DG calls them "ECHO" in some of the
docs). Mine (I have one on my Nova 4 and one on my S/140) are labelled
"6100" for the model.  My controller is labelled "DISC LOGIC NOVA"
10700089102 (you might have to slide the board out to see that
107........ number, but often a flashlight will allow you to see it
while it is still fully in the machine).

> See my website:
> After everything was connected I applied mains. The fans start to run,
> so far so good. Then I switch on the NOVA and then the hard disk unit.
> The POWER LED on the NOVA and on the hard disk is lit. I can hear the
> hard disk "hum", and when the humming sound stops after a few seconds
> the READY LED is lit.

If that is the case, then your hard disk is likely pretty functional (it
may not be fully functional, but the READY light is a very very good
sign).  If the spindle or head lock were present, then I would not
expect that the READY light would come on.

The humming is the spindle startup.  If you hear the disk spinning, then
the spindle is not locked. ;)  If the drive is 100% quiet after the hum
part, then there is probably something not right.  ;)

> However, when I press RESET on the NOVA and then PR.LOAD, the READY LED
> on the disk flashes momentarily (brief), but nothing further happens.

See below regarding the Virtual Console.

> On the disk drive are (behind the panel) two small switches. One has
> the text "NORM" and "PROT", the other has several texts (forgotten),
> but with that switch you can set the hard disk as device 0 and the
> floppy drive device 1, or the hard disk as device 1 and the floppy
> disk as device 0. Basically you can set the boot device, as the machine
> starts from device 0. I have this from the accompanying documentation.

My 6100 is the same.

> When I put that switch in the other position and press RESET and then
> PR.LOAD on the NOVA, the floppy disk LED is lit for a few seconds,
> but I do not hear a head load ("clunk"), nor head stepping sounds.
> Of course, the floppy drive is loaded with a floppy disk. The label
> on the floppy says "opstart" (Dutch for start up). As the floppy disk
> access LED turn on, I guess that I can say that the NOVA itself is OK.
> As far as I know, I have the BERG connector put back on the pins
> where it was before I did the disassembly. That cable connects to the
> terminal. The question might be whether it was on the correct pins
> for starters. I do not get any character(s) on the Dasher D200 terminal
> that came with the system. For that reason, I assume that the terminal
> settings match the settings for the NOVA.

My NOVA/4 has a console ROM (DG calls it a Virtual Console - VC) that
works over the serial port.  That you are seeing no characters is NOT a
good sign.

The Virtual Console on the Nova/4 is very similar to the S/140, so you
can look at bitsavers .../pdf/dg/eclipse in the S140 Programmer's
Reference for guidance.

So, you might start by seeing if the VC is operating.  If it isn't, then
you should presumably fix that first and just leave the disk drive
turned off.

Naturally, the VC "Cells" are different  for the S/140.  For the NOVA 4:

0-3  AC0 - AC3
4    Return address
5    Stack pointer
6    Frame pointer
7    Bit 15 (LSB) Interrupt enable
10   MAP Status word
11   Switch Register
12   Bit 15 (LSB) is the carry bit

My boot sequence from the virtual console on the S/140 goes like this
(the "!" is the Virtual console prompt - see below)

!11A xxxxxx 1000dd<nl> [<nl> is newline - this loads the switch reg.]

where "dd" is the device: 33 for the hard disk or floppy (depending upon
the switch setting) and 22 is mag tape. The leading "1" indicates a
"channel" (DMA) device.  PR Load presumably does essentially the same thing.

> One more remark. On the hard disk is a red label glued. The text on
> it says "remove 2 shipping brackets before operating unit unlock
> pivot arm (see over)". On the rear side of the label is a drawing
> that shows the "front left corner". At the side is a screw (???) to
> lock/unlock the head(s). However, I just don't understand the drawing
> and cannot localize that screw.
> I mailed the previous owner whether he remembers something ...

The spindle lock (shipping bracket, I suppose) is underneath the drive -
where the belt is.  You have to take the bottom cover off of the drive.
 It has two screws on it.  The locked position faces towards the spindle
motor and (I think) a hole in the bracket fits over a locking pin.  The
unlocked position is towards the spindle towards the center of the drive.

The head lock is also underneath the drive - where the belt is.  You
have to take the bottom cover off the drive.  If you follow diagonally
from the motor, past the belt over to the the spindle  and keep going
you will see a little plastic arm, one end of which is on a pin (the
pivot) and the other has (I think) a screw.  The locked position (at
least on a 6100) is toward the middle of the drive, and  the unlocked
position is towards the edge of the drive.

> Anybody has info on the 6101-S2 disk drive? A drawing of those
> shipping rackets, and more info about head locks?

I have doc on the 6100 series, including a copy of the Field Maintenance
manual I can scan it (being a copy, the scan quality won't be as good,
but I'd have to saw my original to scan that in).

I also have a Nova 4/S 4/X field replaceable maintenance manual which
has more info in it than one might think from the title, and probably
has at least some info that would be useful for you (except for the CPU
card itself of course).  This is unbound and would not be difficult to scan.

Finally, I have a Nova 4 programmers reference, but those are bound and
would have to be scanned page by page.

> Thanks,
> - Henk

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