RX50 / RX33 Questions related to PDP-11's

From: Jerome Fine <jhfine_at_idirect.com>
Date: Wed Oct 14 08:32:25 1998

>Zane H. Healy wrote:

> OK, I've got some more questions. It seems I've finally got the PDP-11/73
> I'm working on to talk to the floppy drives. BUT, it won't boot my RT-11
> RX-50 floppies.

Did you make sure that you wrote the boot program:
"COPY/BOOT DU0:RT11FB.SYS DU0:"I assume that you are at least
using V5.3 of RT-11, but I don't remember
when the RQDX3 became supported.

> I'm using the RQDX3 controller as the floppy controller and the WQESD
> (ESDI) controller as the boot device. When I tell the system to boot from
> DUB0 or DUB1 which is the terminalogy that the WQESD controller expects
> (figuring that out, i.e. reading the manual took longer than I want to
> admit) with a RX50 attached, it will access the floppy drives, this is best
> evidenced by my using a cleaning floppy in the drive (made it easy to hear
> the drive being accessed).

An RX50 drive is usually noisy enough even without a disk inside when
it is being accessed for booting. In this case, the controller is being
initialized when the whole PDP-11 was given the initialized signal.

> When I try using a pair of Teac floppies I've converted to RX33's using
> information I found on Sunsite I'm not really sure it tries to access them.
> How do you cable RX33's? I set them to Drive 0 and 1, as the docs said,
> and then used a Y-splitter for the power with a standard PC floppy cable
> (do I need one without the twist?). Can you use RX50 floppies to boot a
> system with RX33 drives?

Are you using a BA23 or a BA123? If you don't have any MFM
hard drives connected, it will probably not matter. Start to check
things out by using an RX50 first. Then switch to the RX33 while
the system is running. That way, you know if your controller is
working OK, etc. I also suggest that when you switch from
RX50 to RX33, you UNLOAD and then LOAD the DU.SYS
device driver. I assume at this point that you are running from the
ESDI drives.

> Will RT-11 boot off of a floppy drive at CSR 17760334? I've tried with
> both the Boot disk from my RX50 distribution set, and a RX50 boot disk that
> I made using PUTR. I've a sinking feeling that having two disk controllers
> is confusing RT-11.

Did you make a second MSCP device driver for the ESDI controller.
That would be the best way. BUT, to do a hard boot, you can't
just re-name the device driver and change the CSR and VECTOR.
The boot block also contains the name of the device driver
as does several other locations and you will have to either SIPP
in the new name or reassemble. At this point, if you don't have
a floppy in the RX50, the DEC BOOT ROMS will hard boot
an alternate CSR for UNIT 0, PARTITION 0. Later, you
can also modify the device driver to boot non-zero partitions
if you are interested. V5.6 already has the code, but previous
versions of RT-11 are missing 1 instruction in the boot code
to be able to do a software boot of non-zero partitions.

> Is it possible to create a Bootable TK50 with RT-11 that can be used to do
> the install?

I believe that is so. I have never done it. It would take longer
to boot than is worth while if it was being done all the time. Better to
make up a bootable RX50 floppy and copy everything to VM:
if you have enough memory.

Sincerely yours,

Jerome Fine
Year 2000 Solutions for Currently Running RT-11 Applications
(Sources not always required)
Received on Wed Oct 14 1998 - 08:32:25 BST