Micro PDP-11

[Cliff Miller]

I have a Micro-PDP11/23+.  Slots 1-3 are KDF11-BA M8189, MSV11-P M8067-LB 512K, and RQDX1 M8639.  The RQDX1 runs an RX-50 which successfully boots RT-11 from floppy.  I've also booted XXDP from a TU-58 simulator on a PC.
My Qbone is on order.  Any thoughts or hints from the group on what slot to place it in?  The box has a H9278A Backplane - I believe the first 3 slots are QBUS - CD so slot 4 and all the rest are Qbus-Qbus.  Also do I need to disable the Hard Drive interface on the RQDX1 in order to boot from the Qbone?

[Ethan Dicks]

On Mon, Sep 19, 2022 at 8:48 AM Cliff Miller <cli...@gmail.com> wrote:
> I have a Micro-PDP11/23+. Slots 1-3 are KDF11-BA M8189, MSV11-P M8067-LB 512K, and RQDX1 M8639. The RQDX1 runs an RX-50 which successfully boots RT-11 from floppy. I've also booted XXDP from a TU-58 simulator on a PC.
> My Qbone is on order. Any thoughts or hints from the group on what slot to place it in? The box has a H9278A Backplane - I believe the first 3 slots are QBUS - CD so slot 4 and all the rest are Qbus-Qbus. Also do I need to disable the Hard Drive interface on the RQDX1 in order to boot from the Qbone?

First, there isn't a separate hard drive/floppy drive controller in
the sense that you are probably thinking. MSCP devices present units
to the operating system, and it doesn't matter if they are disk or
diskette or whatever. You can put multiple MSCP controllers into the
same machine, but there's a set of alternate CSR addresses where boot
ROMs and device drivers expect to see additional MSCP controllers.
The RQDX1 is a funny beast, in general. I don't remember if it can be
strapped to an alternate MSCP address or not, but if it can, you can
restrap it to be the second controller and use the Qbone as the first
MSCP controller. This will change all the disk numbers attached to
it, so if you wanted to boot a real RX50, it might be DU2: or DU3: or
more (depending on how many units the Qbone reports).

If that's problematic, you could leave the RQDX1 alone and tell the
Qbone to report at the alternate address. You would probably then
want to boot DU3: off the Qbone.

Also, the RQDX1 does not pass grant. It has to be the last card in
the machine, always.

I would put the Qbone in the first slot behind memory, and, as you
note, in a Q22-Q22 slot, not a Q22-CD slot.

-ethan

[Jay Logue]

On Mon, Sep 19, 2022 at 5:48 AM Cliff Miller <cli...@gmail.com> wrote:

I have a Micro-PDP11/23+.  Slots 1-3 are KDF11-BA M8189, MSV11-P M8067-LB 512K, and RQDX1 M8639.  The RQDX1 runs an RX-50 which successfully boots RT-11 from floppy.  I've also booted XXDP from a TU-58 simulator on a PC.
My Qbone is on order.  Any thoughts or hints from the group on what slot to place it in?  The box has a H9278A Backplane - I believe the first 3 slots are QBUS - CD so slot 4 and all the rest are Qbus-Qbus.  Also do I need to disable the Hard Drive interface on the RQDX1 in order to boot from the Qbone?

Generally I always place the QBone last, with the exception, as Ethan notes, of any cards that don't pass grant. I found I was not comfortable with having the Qbone sit right below another active card, because of the tight fit and the need to use the plastic sheet to keep things from touching (which I always feared would shift out of place).  As suggested in the documentation, having an interposing M9047 grant card between the Qbone and the previous card makes things feel safer.  However, in your case, this will push you into the H9278's Q22/Q22 slots, so the GRANT continuity jumpers will need to be set accordingly.

--Jay

[Ethan Dicks]

On Mon, Sep 19, 2022 at 11:51 AM Jay Logue <jay....@gmail.com> wrote:
> On Mon, Sep 19, 2022 at 5:48 AM Cliff Miller <cli...@gmail.com> wrote:
>>

>> I have a Micro-PDP11/23+. Slots 1-3 are KDF11-BA M8189, MSV11-P M8067-LB 512K, and RQDX1 M8639...

>
> Generally I always place the QBone last, with the exception, as Ethan notes, of any cards that don't pass grant. I found I was not comfortable with having the Qbone sit right below another active card, because of the tight fit and the need to use the plastic sheet to keep things from touching (which I always feared would shift out of place). As suggested in the documentation, having an interposing M9047 grant card between the Qbone and the previous card makes things feel safer.

I completely agree. Putting a single M9047 in the Q22 side of slot 3
and the Qbone in slot 4 is an excellent idea.

In general, DEC machines are loaded up as CPU->Memory->low-latency
peripherals->high-latency peripherals. There are some specific cards,
like the RQDX1, that make their own rules.

> However, in your case, this will push you into the H9278's Q22/Q22 slots, so the GRANT continuity jumpers will need to be set accordingly.

That as well (though I would have expected a Qbone to usually end up
in a Q22-Q22 slot unless you have a BA11-S - I have a BA11-N I added
BDAL wires to so it's effectively a BA11-S).

-ethan

[Jay Logue]

On Mon, Sep 19, 2022 at 9:01 AM Ethan Dicks <ethan...@gmail.com> wrote:

That as well (though I would have expected a Qbone to usually end up
in a Q22-Q22 slot unless you have a BA11-S - I have a BA11-N I added
BDAL wires to so it's effectively a BA11-S).

Yep.  I run mine in a stand-alone H9276-A backplane (originally from a BA11-S I gather) using a custom power supply.  So it's Q22/CD all the way down.

Unrelated, but another idea which the OP might want to consider, and which I've found convenient, is directly connecting the console to a serial port on the Qbone. This makes it possible to access the console over the network. To keep things tidy, this can be done using a short 10-pin IDC-to-IDC cable with a twist in the middle.  Details on how to make one are here.

--Jay

[Steven Hirsch]

On Mon, 19 Sep 2022, Jay Logue wrote:

> On Mon, Sep 19, 2022 at 9:01 AM Ethan Dicks <ethan...@gmail.com> wrote:
> That as well (though I would have expected a Qbone to usually end up
> in a Q22-Q22 slot unless you have a BA11-S - I have a BA11-N I added
> BDAL wires to so it's effectively a BA11-S).
>
>
> Yep.  I run mine in a stand-alone H9276-A backplane (originally from a BA11-S I gather) using a custom power
> supply.  So it's Q22/CD all the way down.

Sorry if being dumb about this, but is it safe to plug a QBone into a
QBus/CD backplane? I thought that type of mismatch let out magic smoke.

I have an opportunity to pickup a system based on an H9273 backplane and
need to know if this can work.



--

[John H. Reinhardt]

It is.  The QBone has jumpers for configuring it in a Q22/Q22 or Q22/CD quad slot.  The design is such that if you don't change the jumpers nothing bad happens other than it may not pass the bus grant signal with the incorrect jumper setting.  I've had it in both types of slots in my PDP-11/53 and PDP-11/73

--
John H. Reinhardt

[Steven Hirsch]

Oh, terrific. On a slightly related subject, is it possible to emulate a
bootstrap ROM board with QBone? Seems like all the basic capabilities are
there, but I didn't see mention of it on Joerg's web site.



--

[Cliff Miller]

OP here - I’m interested in the topic of bootstrap ROM as well - one application I have is booting an 11/73 cpu (M8192) with no ROM or serial port.

Oh, terrific.  On a slightly related subject, is it possible to emulate a
bootstrap ROM board with QBone?  Seems like all the basic capabilities are
there, but I didn't see mention of it on Joerg's web site.

--

Cliff Miller
cli...@gmail.com

[Joerg Hoppe]

Hi,

to emulate a BDV ROM card for QBUS would be a nice project.
It could be modelled after the M9312 for UNIBUS Unibone.

But bootstrapping  doesn't need a ROM emulation:
MACRO listings of bootloaders can be dumped into memory, then execute
them via ODT to boot.
See the "m ll" commands in these "demo" scripts and listings like
"du.lst", "dl.lst", "dy.lst".

Other bootloader sources to adapt can be found at
https://www.ak6dn.com/PDP-11/M9312/
The code there needs to be separated from the M9312 environment and
assembled to run from RAM, not IOpage.

I ported only the loaders for emulated disks, but others may be helpful too.


kind regards,
Joerg