[Simh] Raspberry Pi 3 with tun/tap causes XQ to fail

[Mark Pizzolato]

On Monday, November 13, 2017 at 2:04 AM, Jeremy Begg wrote:
> I am trying to get SIMH up and running on the ethernet interface of a
> Raspberry Pi 3.  I have followed the intructions in 0readme_ethernet.txt,
> installing the libpcap-dev, bridge-utils and uml-utilities packages before
> building SIMH itself.  I just ran 'make vax' and let it go, and the build to
> completion.
> 
> My problem is that I just can't get networking going.  To cut to the chase, if I
> run the simulator without first setting up the br0 and tap0 interfaces, and
> don't attempt to attach the XQ device, it works fine -- albeit without any
> networking (as expected).
> 
> If I configure SIMH to attach XQ directly to the Pi's eth0 interface (without
> configuring br0/tap0) it works on the first run but fails selftest
> 53 on the next run.  If I reboot the Pi and start the br0/tap0 interfaces and
> then run the simulator the VAX console fails selftest 53 again.

Hmm...  I've been trying to track down the 53 test failure, which I can't reproduce here.
In general this should not have anything to do with the networking details you've got setup, but there might be some influence.

A little background explanation is warranted here.  Long ago, when the extended memory was added to the MicroVAX 3900 simulator (extending from 64MB to 512MB), I had observed that boot ROM self test interval timer test intermittently failed (1 out of 10 times).  At the time, I attributed the failures to competing load on the host system while the timer test was running.  To avoid potential problem reports from users the interval timer tests were disabled with a patch to the ROM image.  The resulting KA655x.bin image was unmodified until this past January.  At that time, the timer related plumbing in simh was significantly reworked and it seemed like the ROM self tests should now pass without the need to side step them.  I re-enabled the tests and, in my testing I've run many hundreds of tests without failure, meanwhile there have been some reports like yours... :-(

Since you've got a somewhat reproducible test 53 failure, will you please:

1) send me the configuration file you're loading
2) send me the ka655x.bin or ka655.bin file you may be loading in your configuration file
3) explicitly load the attached ka655x.bin file prior to booting the simulator in your configuration file with:
         sim> load -r ka655x_test.bin
         sim> BOOT  (or BOOT CPU)
4) let me know if you still can observe the self test problems you had previously seen.

If the problem is completely solved, then I'll revise the packaged (and internal) ka655x.bin ROM image and these problems should be behind us.  If the problem persists, then I'll have to look for other ways to address it.

Thanks.

- Mark
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