Attempting to run 2 drives with mfm emulator

[Jay Cotton]

I have a pdp11/53 with a DQRX3 connected to an mfm emulator.

I can boot from ether disk image, but I can only see one drive.

./mfm_emu --file /disk/rt11_tcpip.hdd,/disk/rt11.hdd --cylinders 820 --heads 6 --drive 2,1

The above emulator command will auto boot from DU1:  After the boot

DU0: is not viewable.  

.dir du0:                                                                      
?DIR-F-Error reading directory       

Yes I have tried all the drive numbers.  And the drive selects are 4 and 3.

Should I be looking at the DQRX3 jumpers ?

JC

[David Gesswein]

On Fri, Jan 31, 2025 at 11:05:25PM -0800, Jay Cotton wrote:
> I have a pdp11/53 with a DQRX3 connected to an mfm emulator.
>

RQDX3.

> I can boot from ether disk image, but I can only see one drive.
>

I assume you are saying that you can boot something like either du0: or
du1:

Are the images different so you can tell that you aren't really booting
the same image with both identifiers?

How were the two images created?

> ./mfm_emu --file /disk/rt11_tcpip.hdd,/disk/rt11.hdd --cylinders 820
> --heads 6 --drive 2,1
>

Command line looks fine. Cylinders and heads are ignored. You only need
to specify them when using --initialize.

> Should I be looking at the DQRX3 jumpers ?
>

Didn't see anything online for the jumpers that seemed related to two drive
usage.

Normally the RQDX3 has an interface board between the controller and the
drives. It normally splits out into separate 20 and 34 pin cables for
each drive. Is that how your system is configured? If so what is the
number of the interface board? Some will need to be modified to use a
single 34 pin cable.

[Jay Cotton]

The two drives have 5.4 on one and 5.7 on the other.

I am using the interface board, its bolted to the chassis behind the

back plane connectors.

I'll have to extract the interface board from the chassis, I'll get back

to you latter today.

jc

[Jay Cotton]

Here is a pix of the interface board p/n

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[David Gesswein]

Found schematic here pg 26 of PDF
http://www.bitsavers.org/www.computer.museum.uq.edu.au/pdf/MP-02028-01%20Rev%20A1%20630QZ%20Field%20Maintenance%20Print%20Set.pdf

DEC didn't do anything strange in the wiring so electrically it should be
fine.

I assume you have it cabled per the manual except only using one 34 pin cable.

http://bitsavers.trailing-edge.com/pdf/dec/pdp11/microPDP11/EK-MIC11-TM-002_MicroPDP11_Systems_Technical_Manual_Sep85.pdf

Not that familiar with PDP-11's. What operating system are you running?
Does it provide any errors hinting at what it thinks is wrong with the
second disk?

Do you still get Error reading directory on second drive if you have mfm_emu
only emulate one drive or does it generate a different error? Wondering if
its really getting a read error or it decided to not try to make the
second drive available.

Any tools to poke at it at a low level and see if it can be accessed?

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[Jay Cotton]

It does not generate an error on the booted drive.  But the other drive (your choice) 

will show a directory read error (i.e. I can't see a thing).  

I am running rt11 vers 5.4 and 5.7 (last version).  They are both rather uninformative 

about error conditions.

The next thing is to get xxdp and the rdqx3 diagnostic package and test the interface.

That may reveal an error condition but may still not show what is busted.   Maybe with

a test loop I can scope a few test points or something.

It might take a few hours to set up a test program.  I have a physical disk with test

code on it.  Gonna be fun.

I'll let you know if I find anything.

jc

[Jay Cotton]

Did check all the jumpers on the board.  It matches the installation manual.

However, I managed to break the board while I was putting it back in.  So, new

board on order.

[hupfadekroua]

Hi,

a general question:

how did you configure the pdp11 setup?

Which adresses did you use.

I never got the emulator working on a 53 or 73.

Could you provide the disk images?

Best

Andreas

Am 03.02.2025 um 08:02 schrieb Jay Cotton <lbmg...@gmail.com>:

Did check all the jumpers on the board.  It matches the installation manual.

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[Jay Cotton]

Location of working copy of rt11 5.4 rqdx3 controller  rx33 disk.

https://github.com/jayacotton/pdp11-build

mfm emulator command 

./mfm_emu --file /disk/rt11_tcpip_backup.hdd --drive 2  

JC

[Rob Pritchard]

Appreciate this is an old thread, but I have MFM Emu working find with an RQDX3 in an 11/73 I’m recommissioning. I’m not sure you’ll be able to use dual drives unless you have a 6 button control panel (I’m assuming you’re using a BA23 chassis).

Rob.