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

[Paul Koning]

> On Mar 22, 2018, at 6:15 AM, Phil J Fisher <phil.fisher at peejayeff.co.uk> wrote:
> 
> Hi
> 
> can anyone suggest what I have done wrong or what I am missing?
> 
> I am running SIMH 3.9 (from the SimH site) on a Centos6 system run under VMware (also VirtualBox gives same results).  I have been using Bob Evans RSX11M information from his site.
> When I load the simulator using mostly his sim.ini file (I removed his telnet stuff that was built in) and type the usual 'BOOT RL0' (or 'boo rl0') I get a Halt at PC 0.
> Examining the code at location 0 I get (as expected from output) a HLT instruction (000000 octal).
> 
> The disk images do not appear to be corrupted but I am not aware of any MD5 or similar checksums to be certain.

A simple check would be to look at the first block of the image you have attached to the drive you're booting.  Try "hexdump -0 -n 512".  You might see something like this:

$ hexdump -o -n 512 ~/Documents/e11/v101du.dsk
0000000  000240  000572  000006  000000  000012  000000  000020  172150
0000010  052504  012707  054464  000000  001570  021041  000041  000000
0000020  000000  000000  000000  000606  000471  010705  062705  000344
0000030  012700  000064  005025  077002  016767  177740  000436  016767
0000040  177734  000454  016767  177730  000450  016767  177730  000420
...

A reasonably new PDP11 disk has a boot block starting with 000240 (NOP).  If it's old it might just start with something executable, like this RSTS V4 (1972 vintage) system disk:

$ hexdump -o -n 512 ~/Documents/e11/v4.dsk 
0000000  012700  000024  016701  000162  010104  012021  020027  000200
0000010  001374  010407  162701  000020  012702  000005  000005  010704
...

If it starts with 0 but the word after contains what looks like PDP11 code, it could be a disk for a PRO, though that would be a bit odd and certainly would not be the case for an RL02 image.

	paul