[Simh] VAX emulation issues on Raspberry Pi

[Timothe Litt]

Two issues have been discussed before.

The boot failures are being worked by Mark - they're some timing issue
having to do with the fact that SimH is faster than the hardware.  They
seem to be a heisenbug.  He's recently added instrumentation.

The SSH startup isn't compute bound so much as entropy limited.  This
was discussed a while ago, but I don't recall the final outcome.  Check
the archives.

The 4000/96 would be a NVAX or NVAX+.  It would require more license
units than the 3900, so I'm somewhat surprised that you're having
issues.  But LMF has lots of ways to evaluate licenses.  The SID
register reflects the CPU type; SYS_TYPE has the licensing bits.  The
SID determines which VMS CPULOA is loaded - this is what I/O buses are
supported, machine check format - you can't change it without a lot more
grief.  The SYS_TYPE bits are the workstation vs. server.  There's SimH
support for that.

On 30-Jul-18 18:57, Jeremy Begg wrote:
> Hi,
>
> A while ago the power supply in my VAXstation 4000/96 died and rather than
> fix it I decided to move it to a Raspberry Pi 3.
>
> The VAXstation has a 100MHz CPU and the RPi has a 1.2GHz CPU - about 120
> times faster.  Yet the performance of SIMH basically sucks, especially when
> logging in to the emulated VAX via SSH.
>
> On the real VAXstation, establishing an SSH sesison was slow -- it would
> take the better part of a minute -- but once established it was very usable
> and quite capable of running a DECterm to an X11 display on a remote PC over
> an SSH tunnel.
>
> On the Raspberry Pi the SSH session establishment takes several minutes and
> trying to run a DECterm is painful to say the least.  I was hoping that the
> RPi's much faster CPU would compensate for the emulation overhead,
> particularly on a very CPU-intensive task like SSH session establishment, so
> this result is rather disappointing.
>
> I could perhaps put up with those issues but there two other, more
> fundamental problems when starting the simulation.
>
> The first one is, the emulation can't be started automatically; I have
> to run it interactively in a terminal window.  If I try to automate the
> startup using, for example
>
>    $ ./vax < vax.ini
>
> the VAX console boot ROM fails a self test and refuses to boot into VMS.
> If I type the commands from vax.ini by hand, it works fine.
>
> A similar issue occurs if I try to load the boot console NVR from a file:
> the VAX console boot ROM fails its self-test and won't boot VMS.
>
> The second problem is that the simulated VAX is *always* a VAXserver 3900. 
> Trying to SET CPU MODEL=MicroVAX just doesn't work, so my VAX-VMS licence
> PAK's availability table code don't suit the machine any more.
>
> The SIMH version is currently 
>
>    MicroVAX 3900 simulator V4.0-0 Beta       git commit id: 733ac0d9
>
> I tried downloading the latest from Github (git commit id: 8077d4de) but it
> didn't fix the startup issues so I haven't persisted with it.
>
> Before starting this exercise I had read several reports of people
> successfullly using Raspberry Pi to run an emulated VAX so I have to think
> something is very broken in my RPi environment, but I'm not sure what I
> should be looking for.
>
> FWIW the Raspberry Pi is running
>
> Linux pieric 4.14.52-v7+ #1123 SMP Wed Jun 27 17:35:49 BST 2018 armv7l GNU/Linux
>
> and the file /etc/os-release is:
>
> PRETTY_NAME="Raspbian GNU/Linux 9 (stretch)"
> NAME="Raspbian GNU/Linux"
> VERSION_ID="9"
> VERSION="9 (stretch)"
> ID=raspbian
> ID_LIKE=debian
> HOME_URL="http://www.raspbian.org/"
> SUPPORT_URL="http://www.raspbian.org/RaspbianForums"
> BUG_REPORT_URL="http://www.raspbian.org/RaspbianBugs"
>
> SIMH was built with "gcc (Raspbian 6.3.0-18+rpi1+deb9u1) 6.3.0 20170516".
> Here is the full SHOW VERSION output:
>
> sim> show version
> MicroVAX 3900 simulator V4.0-0 Beta
>     Simulator Framework Capabilities:
>         64b data
>         64b addresses
>         Threaded Ethernet Packet transports:PCAP:TAP:NAT:UDP
>         Idle/Throttling support is available
>         Virtual Hard Disk (VHD) support
>         RAW disk and CD/DVD ROM support
>         Asynchronous I/O support (Lock free asynchronous event queue)
>         Asynchronous Clock support
>         FrontPanel API Version 5
>     Host Platform:
>         Compiler: GCC 6.3.0 20170516
>         Simulator Compiled as C arch: ARM (Release Build) on Nov  9 2017 at 08:04:00
>         Memory Access: Little Endian
>         Memory Pointer Size: 32 bits
>         Large File (>2GB) support
>         SDL Video support: No Video Support
>         RegEx support for EXPECT commands
>         OS clock resolution: 1ms
>         Time taken by msleep(1): 1ms
>         OS: Linux pieric 4.14.52-v7+ #1123 SMP Wed Jun 27 17:35:49 BST 2018 armv7l GNU/Linux
>         git commit id: 733ac0d9
>
> The later version (which I'm not running because it didn't fix the startup issues) is:
>
> sim> show version
> MicroVAX 3900 simulator V4.0-0 Current
>     Simulator Framework Capabilities:
>         64b data
>         64b addresses
>         Threaded Ethernet Packet transports:PCAP:TAP:NAT:UDP
>         Idle/Throttling support is available
>         Virtual Hard Disk (VHD) support
>         RAW disk and CD/DVD ROM support
>         Asynchronous I/O support (Lock free asynchronous event queue)
>         Asynchronous Clock support
>         FrontPanel API Version 12
>     Host Platform:
>         Compiler: GCC 6.3.0 20170516
>         Simulator Compiled as C arch: ARM (Release Build) on Jun 17 2018 at 21:12:47
>         Memory Access: Little Endian
>         Memory Pointer Size: 32 bits
>         Large File (>2GB) support
>         SDL Video support: No Video Support
>         RegEx support for EXPECT commands
>         OS clock resolution: 1ms
>         Time taken by msleep(1): 1ms
>         OS: Linux pieric 4.14.52-v7+ #1123 SMP Wed Jun 27 17:35:49 BST 2018 armv7l GNU/Linux
>         git commit id: 8077d4de
>         git commit time: 2018-06-17T08:37:08+02:00
>
>
> Thanks,
>
>         Jeremy Begg
>
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