RT-11 / RX-01 issues ... "almost" boots ... - test-drb@ccmp.vtda.org

20 Apr 2011

The original RAM configuration is outlined below.  It was used this way, and booted just
fine from RK-05's in days gone by.

An M7847 with 16KW
A Motorola board with 6 rows of 9 4116 chips (for a total of 48KW)
A Mostek board with eight rows of 9 4116 chips (for a total of 64KW)

The Motorola board was originally set to the lowest 48K, the M7847 after that, and the
Mostek for the highest 64KW addresses ... I reconfigured when I checked these out (I lack
the actual docs on the Motorola and Mostek boards but there are only eight DIP switches so
it was easy enough to guess and just verify the range via the front panel ... bus error
when a non-existent address is deposited).

I think I goofed on the original size of the Mostek board ... it sports two banks of 4
rows by 9 of 4116 chips (64KBytes each bank).

As for the RX11 interface (M7846),  I could not find config info except for a photo of a
board on the web (checked bitsavers but can't find that board).  My jumpers are as
follows: V2 V4 V5 V7 N1 A7 A8.  All other jumpers are snipped off.

Power Supply: after the long-term storage in the garage that was the first thing I
checked.  Once had a 5V supply put out 7V so I'm paranoid about that now!  The 5V and
+/- 15V supplies are all good.

Cheers .... Mark

Professor Mark Csele, P.Eng.
Niagara College, Canada
300 Woodlawn Rd., L-23
Welland, ON, L3C 7L3

(905) 735-2211 x.7629
E-Mail: mcsele at niagarac.on.ca
URL: http://technology.niagarac.on.ca/people/mcsele
Author of "Fundamentals of Light Sources and Lasers", Wiley, 2004
...
  > Tony Duell
<ard at p850ug1.demon.co.uk> 04/19/11 5:47 PM >>>  
 Well, a few more bizarre things to report:

 I tried to disable interrupt sources as suggested.  The only one, =
 apparently, was the DL11-W SLU/LTC card which was set for both functions.  =
 The card was reconfigured to be "SLU Only".  No change in behaviour.  The =
 DL11-W console is set for address 177560, vector 60. 
The console will geneate 2 iterrupt vectors (60 and 64 I think) for 
transmit and receive. They cannont be set separately, so if the DL11-W is 
working properly, that's OK.

The RX11 will also generate interrupts. What's it set to?

...

 Next, there are three memory cards: one M7847-DJ (16K*18 MOS, MS11-JP), =
 one "Motorola memory systems" card with 48K words, and one "MOSTEK memory
=
 systems" card with 96K words.  Both the two later cards use 4116 DRAM =
 chips. 
Hang on a second. You've got 16Kw + 48Kw + 96kw there. That's 160Kw 
total. The PDP11/34 (it is an 11/34 IRIC) has 18 bit addressing and can 
access a total of 128kw. 4Kw are used for the I/O space, so you have have 
a maximum of 124kw of memory (practically, most memory boards wil 
lautomatically disable themselves in the I/O space, so you could fit a 
pair of 64Kw boards, say,m without problems). But with your configuration 
you must have some locations addressing 2 boards, which is not a good thing.

...

 Tried to use the M7847-DJ card alone (after all, RT-11SJ should run on =
 16KW of memory).  Reconfigured the card address to start at 0 and verified =
 that it occupies addresses 000000 to 077777 via the front panel.  When the =
 machine it turned on, the display reads "054207" (this was not expected).  =
 Tried booting using the bootstrap on the M9301-YB card: the heads don't =
 engage at all and the program halts rapidly displaying "173764" ... =
 BIZARRE since that is a non-existent address. 
Is it? Remeebr the address show is the 16 bit program counter address. If 
the MMU is disabled (which it will be on power-up, and nothing is going 
to enable it), addresses starting 16 or 17 are mapped to the I/O space at 
76 or 77. So that address is 773764. Which I think is in the bootstrap 
ROM. 

...

 Next, tried the Motorola memory card which was already configured to start =
 at 0.  When the CPU is powered-on, displays "000002" on the display.  =
 Tried to boot the disk, heads engage, a few steps of the disk heads, and =
 halts again at "005134".

 Finally, tried the MOSTEK memory card.  Reconfigured to start at 0, and =
 verified that addresses 000000 through 377777 are occupied by RAM.  Powers =
 up with a display of 000002 and halts at 005134 when a boot is attempted.

 The system is now stripped during testing, consisting of the following:
 Slot 1/2 =3D CPU, Slot 3=3DM7859 Panel interface and M9301-YB bootstrap/ter=
 minator, Slot 4=3Dmemory, slot 5&6&7 empty (with a grant continuity card =
 in D), slot 8=3DM7856 SLU/LTC, slot 9=3DM9302 at the unibus end and M7846 =
 RX-01 interface. 
That sounds OK.

...
  As I was typing this, had a thought about slots: I
recall reading =
 something about not putting memory into slot 9.  So, I moved the RX-01 = 
Yes, The reason is that memroy boards are MUD (Modified Unibus Device) 
boards and take their signals from connectors A,B (this matters on 
machines like the 11/44 which have a 22 bit address bus, and where the 
addres lines on A,B are not the same as those on E). Device controllers 
(SPCs -- Small Peripheral Controller) take their signals from C-F. On 
slot 9, the A/B conenctors are the Unibus output to the next backplane 
(or for a terminaotr) and are not qurie the same signals as the ones on 
an MUD slot. In fact I think on some machines you can short out a power 
rail by putting  an MUD card in the Unibus Out slot or a termintor in an 
MUD slot.

...
  controller to slot 6 (and moved the grant card in slot
9D).  Now, when =
 powered-up with the Motorola or Mostek memory cards, displays "000000" but =
 otherwise no changes in booting behaviour.  When the MS11-JP RAM was =
 installed instead, displays "177777" once, "163776" the next time
(when =
 powered up), and still absolutely nothing when boot is attempted (i.e. no =
 heads engaging at all).

 Is there something about RT-11 5.04 that I am not aware-of?  An it was =
 suggested that there is a difference between the Unibus and Q-Bus boot ... =
 any thoughts on that one? =20 
I've never heard of that being a problem...

...

 I can't see memory being the issue anyway: sure, 16KW might be an issue =
 (and that card might even be 'flaky'), but the other two cards are large =
 enough. 
Silly question... Whenever I hear of a PDP11 wit flaky memeory I think of 
the time I was led a merry dance by my 11/45. It turns out the problem 
ther was power supply related (one ofthe 5V lines was sitting at 4.4V). 
Have tyoy checked all the power supply voltages with the machine in 
operation?

-tony