[Simh] XXDP V2.2 problems.

[Mattis Lind]

I have some troubles running a known working XXDP V2.2 image in SimH on a
11/23 (without +), 11/03, 11/04, 11/05 and 11/20.

I have tested this on a PDP-11/44 and a PDP-11/23+ CPU and it works fine.
Testing the same image in SimH on 11/23+ and 11/44 config with 64kbyte
memory starts the XXDP fine.

https://dl.dropboxusercontent.com/u/96935524/xxdp.dsk

Now I have to be honest. I am not entirely sure which CPU configs should be
able to run XXDP V2.2 (Small Monitor).

But I basically thought that switching to 11/23 (without plus) should work
fine since it is very similar to the plus. Just removing the two SLUs and
the Boot ROMs would make it identical as far as I can see it.

But it doesn't start.

sim> b rq0


HALT instruction, PC: 000104 (JMP SP)

Doing a continue actually makes it to boot:

sim> c

NOT ENOUGH MEMORY TO BOOT XXDP-XM



BOOTING UP XXDP-SM SMALL MONITOR



XXDP-SM SMALL MONITOR - XXDP V2.2
REVISION: C0
BOOTED FROM DU0
28KW OF MEMORY
NON-UNIBUS SYSTEM

RESTART ADDR: 152010
TYPE "H" FOR HELP

.

But it is not entirely happy since the very simple GKAAA0 cpu test that
runs fine in 11/23+ mode fails.

.R GKAAA0
GKAAA0.BIC

HALT instruction, PC: 000104 (JMP SP)
sim>

I know that SimH is not supposed to be able to run the diags but what is
the difference on a SimH level between 11/23 and 11/23+ that causes one to
run and the other not?

Then I tested some other CPUs:

11/34, 11/40, 11/44, 11/45, 11/60, 11/70, 11/73, 11/83, 11/84, 11/93

The all can start XXDP V2.2 (SM) and run GKAAA0 fine.

But

11/03 and 11/23 give me the halt. In the 11/03 case it is not possible to
do a continue.

Testing 11/04, 11/05 and 11/20 all give the same result. It never boots but
gets stuck in some loop where it seems to poll the console.

Step expired, PC: 150674 (BPL 150750)
sim> s

Step expired, PC: 150750 (MOV (SP)+,R1)
sim> s

Step expired, PC: 150752 (RTS PC)
sim> s

Step expired, PC: 151006 (TST R0)
sim> s

Step expired, PC: 151010 (BEQ 151002)
sim> s

Step expired, PC: 151002 (JSR PC,150664)
sim> s

Step expired, PC: 150664 (CLR R0)
sim> s

Step expired, PC: 150666 (MOV R1,-(SP))
sim> s

Step expired, PC: 150670 (TSTB @#177560)
sim> s

Step expired, PC: 150674 (BPL 150750)
sim> s


SimH is built from head:

sim> sh ver
PDP-11 simulator V4.0-0 Beta
Simulator Framework Capabilities:
32b data
32b addresses
Ethernet Packet transports:PCAP:NAT:UDP
Idle/Throttling support is available
Virtual Hard Disk (VHD) support
Asynchronous I/O support
FrontPanel API Version 1
Host Platform:
Compiler: GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.2.76)
Simulator Compiled: Dec 27 2015 at 17:51:17
Memory Access: Little Endian
Memory Pointer Size: 64 bits
Large File (>2GB) support
RegEx support for EXPECT commands
OS clock resolution: 1ms
Time taken by msleep(1): 2ms
OS: Darwin localhost 12.5.0 Darwin Kernel Version 12.5.0: Sun Sep 29
13:33:47 PDT 2013; root:xnu-2050.48.12~1/RELEASE_X86_64 x86_64

        git commit id: ea4d9a16

Tested SimH 3.9 and it does the same

11/04, 11/05 and 11/20 all lack MMU if this has to do with it. But 11/03
also lack MMU and is not behaving the same, although not booting. The 11/23
has the MMU but is still not booting while the almost identical 11/23+
boots just fine.

Well. If someone can help me sort this out I am would be happy. My next
step is to try to boot the same image on a real 11/04, 11/03 and a 11/23
(without +) to see if that works. Just need to toggle in that long
bootstrap.

/Mattis
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