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11/73 question.

My diagnostic plan is as follows:

1. Remove the RD52 hard drive. Avoid any potential conflict with the RX50 drives.
2. Check the voltage supplies to the drive cables.
3. Reinstall link W23 as I found it originally.
4. Just seen the LED on the RQDX3... This LED should illuminate on a RESET and should extinguish if the self test is OK.
5. I have spare RX50 drives - so I could replace the RX50 drive for another.
6. I would then replace the RQDX3 with an RQDX1.

Hopefully, one of these actions should result in an operational system.

In the meantime, I will read up further on QBUS bus priority slot allocation...

Dave
 
If you swap the RQDX3 for a RQDX1 you will need to reformat the RD52.
Not if I am going to remove the RD52 (list item 1)...

I am aware that I would have to reformat it if I am going to use it through...

The entire purpose of getting this machine up and running is to erase a number of disk drives before I send them on to people. This is a requirement of the industry I work in. I have a SCSI disk controller to use for myself.

Dave
 
Time to fire up your trusty uVAX-2000. I think it's the only dec product that can easily format RD-media.
 
OK, so no further forwards with a 'fix' - but a load more data points to pinpoint what is potentially wrong!

I found that I had incorrectly connected the RD52 up. I had connected the control cable to the connector for "fixed drive 1" and the data cable to the connector for "fixed drive 0". Fixed that - still no joy with the RD52 or RX50.

I disconnected the RD52 - still no joy with the RX50.

I tried another RX50 disk drive unit - still no joy with the RX50.

I measured the voltage on both disk power connectors - +5V and +12V all present and correct.

From the above I conclude that the problem is unlikely to be the drives themselves.

I then turned my attention to the controllers.

I tried the original RQDX3, two (2) off RQDX1 and a CMD SCSI controller - all with the same results. I have tried the RQDX3 and RQDX1 both with and without the disks connected. I had no disks connected to the CMD SCSI controller.

I reorganised the cards in the backplane to make sure it wasn't that. I have them in the following order:

SLOT 1 - 11/73 QUAD CPU.
SLOT 2 - DLV11-J DUAL SERIAL.
SLOT 3 - 256KB DUAL RAM.
SLOT 4 - DISK CONTROLLER. RQDX3=DUAL. RQDX1=QUAD. CMD SCSI=DUAL.

The DLV11-J and 256KB RAM cards are dual-height and are installed in the Q22 slots. C/D slots 2 and 3 are not occupied.

I noticed that when I attempted to BOOT from any of the DU devices (with the RQDX3 or RQDX1's) - that the front panel RUN LED extinguished.

I also tried to load the internal diagnostics/utilities from the CMD SCSI controller and found an interesting issue. Using ODT I could deposit 123456 into 17772152. As soon as I deposited 100 into 17772152 - the front panel RUN LED extinguishes and the machine 'locks up' (i.e. I don't get the ODT '@' prompt back).

From this I am thinking that the problem is DMA accessing. Once I have written the 'magic numbers' to the CMD SCSI controller - it should DMA the diagnostics/utility code into main memory. I assume it is this that is going horribly wrong.

I am suspecting that the CMD SCSI controller is requesting the bus, the CPU is granting the controller bus access - however the CMD SCSI controller is not seeing the bus being granted to it. As a result, we have a 'deadly embrace' in that the disk controller is waiting for the CPU to relinquish the bus and the CPU has relinquished the bus and is waiting for the controller to finish.

As I have already found one PCB track that was damaged on the 11/73 CPU card - I will look for some further ones associated with the DMA request/grant signals:

BDMGI on AR2
BDMGO on AS2
BDMR on AN1
BSACK on BN1

Anyone any further thoughts?

Dave
 
Last edited:
I'm
I reorganised the cards in the backplane to make sure it wasn't that. I have them in the following order:

SLOT 1 - 11/73 QUAD CPU.
SLOT 2 - DLV11-J DUAL SERIAL.
SLOT 3 - 256KB DUAL RAM.
SLOT 4 - DISK CONTROLLER. RQDX3=DUAL. RQDX1=QUAD. CMD SCSI=DUAL.
I'm accustomed to having the controller closer to the CPU than the SLU, which means the RQDX3 or a bus grant card to get the RQDX1 into the later slots. I doubt it's going to change anything, but it's something I'd try since the overhead is low.
 
I checked my notebook and did have the scenario where I had CPU (slot 1), CONT (slot 2 AB), 256KB RAM (slot 3 AB) and then the RQDX1 and RQDX3 disk controller (slot 4).

No dice.

Dave
 
I'd still recommend giving vtserver a try, but an alternative would be to try TU58FS as a way to get an OS loaded and poke around in the system. It will connect to your DLV11 and give you a way to run XXDP and RT-11, from which you can inspect the vectors and addresses going on with the system as well as potentially just use to init the drive(s).
I'm not seeing the usual site, but Guy has a copy for download: http://www.shiresoft.com/pdp-11/software/vtserver.html
 
Dave, I have a similar system, using some parts you kindly helped me with, My current set up is..

slot 1 M8367 pmi memory card ( quad)
slot 2 M8367 pmi memory card ( quad)
slot 3 M8190 cpu (quad)
slot 4 M7555 rqdx3 ( AB) ....M9047 ( CD)
all other slots unused
console is via the M8190 with the correct baud rate selector rear panel, set to 9600, connected via the single console output socket.

I only have dual floppy drives fitted, and can boot from DU0. no prob. ( if I recall in my setup, DU0 = top A 5.25" drive, DU1 = bottom B 5.25" drive)

Don't have the answers to your problems , but this set up works for me ,with out a hard drive fitted. ( not yet)

Harry
 
Dave,

Did you get your 11/73 working? I am only down the road, a couple on junctions on the M5 and have a working Micro 11/73. If you like we could meet up and you can try your boards in my system / mine in yours.

Peter
 
It was the CPU board in the end...

I fixed the faulty address line that had become damaged, but I could never get to the root cause of why the CPU was locking up when I tried to boot from a disk controller.

I replaced my quad height 11/73 CPU with a dual height one and all appears to be well with the world.

I have just got bogged down with work now and I have had to put the PDP project on hold for a short while.

Just taken delivery of a SCSI disk emulator.

Dave
 
And thanks to TasKiNG for the replacement CPU board (since I gave away all of my other ones)!

Finishing off the SBD DMA driver is on hold as well of course...

Dave
 
Hi, you want to have the CPU in the top slot and no gaps, but follow the IRQ path as per the BA23 manual... otherwise you will be getting odd and undefined behaviour...

Drop me a PM or we can discuss it more!
 
I know all about the 'special' slots 1/2/3 and 4-8 serpentine etc. It is nothing to do with that I am afraid...

Since you are only just north of me, perhaps we can have a beer and a curry one night?

Dave
 
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