RT11 V4 on 11/2 halts at 1002 at boot time

[Lee Gleason]

I've been playing around with some old QBUS parts here, with an eye
to assembling a small desktop system. I loaded a KD11-HA (LSI-11/2) and
an M8047-CA (MXV11-AC) into a BA-11VA (4 slot "leprechaun box").

Using a TU58 emulator, this will successfully boot any of the several
XXDP TU58 images I have (via 173000G).

Testing with ODT shows the MXV11 RAM is present and goes from 0 to
32K. I figure the boot roms are OK and mapped at the right place,
because it boots XXDP fine.

I wanted to see if it could run RT-11. I created a TU58 image of RT11
V4 (it's what I had laying around), using SIMH. This image will boot and
run fine in SIMH, with SIMH set to CPU 11/03 and 32KB. But, when I try
to boot it into the 11/2 system, it loads a few blocks, and then halts
at 1002 - console just says @1002.

Any suggestions as to what could be tripping me up here?

--
Lee K. Gleason N5ZMR
Control-G Consultants
***@comcast.net

[Ian Hammond]

Post by Lee Gleason
I've been playing around with some old QBUS parts here, with an eye
to assembling a small desktop system. I loaded a KD11-HA (LSI-11/2) and
an M8047-CA (MXV11-AC) into a BA-11VA (4 slot "leprechaun box").
Using a TU58 emulator, this will successfully boot any of the several
XXDP TU58 images I have (via 173000G).
Testing with ODT shows the MXV11 RAM is present and goes from 0 to
32K. I figure the boot roms are OK and mapped at the right place,
because it boots XXDP fine.
I wanted to see if it could run RT-11. I created a TU58 image of RT11
V4 (it's what I had laying around), using SIMH. This image will boot and
run fine in SIMH, with SIMH set to CPU 11/03 and 32KB. But, when I try
to boot it into the 11/2 system, it loads a few blocks, and then halts
Any suggestions as to what could be tripping me up here?
--
Lee K. Gleason N5ZMR
Control-G Consultants
--
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The RT-11 primary bootstrap executes in the first 256-words of memory. The primary bootstrap reads the secondary bootstrap into memory beginning at location 1000 and then jumps to location 1000 to start it.

My first guess is that the secondary bootstrap read must have failed, leaving location 1000 at its start-up value of zero, which is also the HALT instruction code. When the machine stops it displays the location just past the halt instruction, which is 1002.

However, since you say that the same tape works with SimH and that you've loaded XXDP systems successfully I can't see why the read should have failed, particularly since you say it read more than the one block necessary for the primary boot.

BTW: it's always a good idea to switch of the PDP-11 clock when debugging boot operations.

[Lee Gleason]

Post by Ian Hammond

Post by Lee Gleason
I've been playing around with some old QBUS parts here, with an eye
to assembling a small desktop system. I loaded a KD11-HA (LSI-11/2) and
an M8047-CA (MXV11-AC) into a BA-11VA (4 slot "leprechaun box").
Using a TU58 emulator, this will successfully boot any of the several
XXDP TU58 images I have (via 173000G).
Testing with ODT shows the MXV11 RAM is present and goes from 0 to
32K. I figure the boot roms are OK and mapped at the right place,
because it boots XXDP fine.
I wanted to see if it could run RT-11. I created a TU58 image of RT11
V4 (it's what I had laying around), using SIMH. This image will boot and
run fine in SIMH, with SIMH set to CPU 11/03 and 32KB. But, when I try
to boot it into the 11/2 system, it loads a few blocks, and then halts
Any suggestions as to what could be tripping me up here?

The RT-11 primary bootstrap executes in the first 256-words of memory. The primary bootstrap reads the secondary bootstrap into memory beginning at location 1000 and then jumps to location 1000 to start it.
My first guess is that the secondary bootstrap read must have failed, leaving location 1000 at its start-up value of zero, which is also the HALT instruction code. When the machine stops it displays the location just past the halt instruction, which is 1002.
However, since you say that the same tape works with SimH and that you've loaded XXDP systems successfully I can't see why the read should have failed, particularly since you say it read more than the one block necessary for the primary boot.

Thanks for the info. It turned out that there was a problem with the
TU58 emulator, that caused bad data to be stored. I cleared that up and
it worked fine.

--
Lee K. Gleason N5ZMR
Control-G Consultants
***@comcast.net