[Simh] Problem booting RSX11M on pdp11 (halt at loc 0)

[Phil Fisher]

Dear SimH people

I think I have found a pointer to the issue. The issue apparently being that my VirtualBox simulator under which I run Centos 6 Linux seems to have some challenge providing disk information to the SimH simulator running on Centos 6.

I think I have demonstrated this by first enabling some debugging on the compiled pdp11 simulator (DEBUG=1) and enabling DEBUG=TRACE;OPS;DATA on the RL disk device.

When I ran the simulator and merely enabled 11/70, 1MB RAM and a RL0 disk attached, I found the following results (the last few lines only shown):

PDP-11 simulator V4.0-0 Current        git commit id: 9111a1a6
======================================================================
Disabling XQ
CPU     11/70, FPP, RH70, autoconfiguration enabled, idle enabled
        1024KB
...
sim> attach RL0 ./RSX-11M_V3.2_RSX11MBL26_3.2.rl01
sim> BOOT RL0
DBG(8281)> RL RWR: >>RL wr: RLDA 000013
DBG(8281)> RL RWR: >>RL0 write: RLBA=013
DBG(8283)> RL RWR: >>RL wr: RLCS 000200 new 000004
DBG(8283)> RL RWR: >>RL GSTA: rlds=000035 drv=0
...
DBG(8320)> RL RRD: >>RL0 read: RLCS=014
DBG(8322)> RL RRD: >>RL rd: RLCS 000014
DBG(8322)> RL RRD: >>RL0 read: RLCS=014
DBG(8324)> RL RRD: >>RL rd: RLCS 000014
DBG(8324)> RL RRD: >>RL0 read: RLCS=014
DBG(8325)> RL OPS: >>RL svc: func=RD drv=0 rlda=000000
DBG(8325)> RL OPS: >>RL svc: cyl 0, sect 0, wc 512, maxwc 5120
DBG(8325)> RL OPS: RL0 sim_disk_rdsect lbn: 00000000 len: 00000400
DBG(8325)> RL OPS: 0000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
DBG(8325)> RL OPS: 0010 thru 03FF same as above
DBG(8326)> RL RRD: >>RL rd: RLCS 000215
DBG(8326)> RL RRD: >>RL0 read: RLCS=0215
DBG(8328)> RL RRD: >>RL rd: RLCS 000215
DBG(8328)> RL RRD: >>RL0 read: RLCS=0215
DBG(8328)> RL RWR: >>RL wr: RLCS 000215 new 000000
DBG(8328)> RL RWR: >>RL0 write: RLCS=00

HALT instruction, PC: 000002 (HALT)
sim>

at which point clearly the BOOT RL0 command will fail (and HALT).
So the buffer returned from the disk is all zeroes and is loaded into memory which results as above.

I had a think and considered that perhaps the I/O in the simulator(s) was getting confused somehow.  So I attached the SAME DISK IMAGE but fetched it from the local PC store by making use of the Shared Folder feature of VirtualBox.  This led the disk image to be located on the NTFS Win 10 filestore.

And lo, behold!  It boots and I get the RSX11M prompt.

sim> SET RL  ENABLE
sim> SET RL0 ENABLE, RL01, WRITEENABLED
sim> set RL DEBUG=OPS;TRACE;DATA
sim> ATTACH RL0 /mnt/phil/phil_dir/Simulators/rsx3_2/rsx11mbl26_3_2.rl01
RL0: '/mnt/phil/phil_dir/Simulators/rsx3_2/rsx11mbl26_3_2.rl01' Contains an ODS1 File system
RL0: Volume Name:       RSXM26 Format: DECFILE11A   Sectors In Volume: 10240
sim> boot RL0


  RSX-11M V3.2 BL26   28K
>RED DL:=SY:
>RED DL:=LB:
>MOU DL:RSXM26
>@DL:[1,2]STARTUP
>* PLEASE ENTER TIME AND DATE (HR:MN DD-MMM-YY) [S]:

Notice that SimH detects it as a native File11 file system whereas before the format was apparently SimH based on simulator output.

Now, given the above, has anyone any suggestions on how I look further on this on the grounds that I would like the setup to be as normal as possible and using "native" files in the VBox/Centos6 system?

Phil
--
Phil J Fisher           phil.fisher at peejayeff.co.uk
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