[Simh] SimH VAX cluster connect timeouts

[paulhardy2 at btinternet.com]

At home I run a  hobbyist VMScluster with three SimH VAX instances - the
boot node MicroVAX HARDY1 is on an Intel i5 NUC running Windows 10, one
VAXStation satellite is Raspberry Pi 3, and I recently added a second-hand
Intel I5 PC running Debian (Raspberry desktop) called HARDY3 as another
satellite VAXStation.

When I network boot the Debian satellite HARDY3, it gets its boot from
HARDY1, and then repeatedly says "%VAXcluster, no connection to disk server"
with no pauses, and then crashes. See log below.

I suspect this due in some way to the speed of the networking interface of
the Debian host (Gb Ethernet) - on a real VAX there would be a significant
pause between these messages if the connection was not established
immediately. On the Raspberry Pi, I sometimes get a few of these messages
before the connection is established.

I tracked down that SimH has a SET XQ THROTTLE command, but trying SET XQ
THROTTLE=ON didn't seem to help. I then saw that the XQ THROTTLE has three
further parameters, TIME, BURST and DELAY with default values of 5, 4 and
10, so I tried SET XQ THROTTLE=TIME=10;BURST=2;DELAY=20, and after 16 rapid
"no connection" messages, it did connect, and VMS booted and ran normally. I
did feel that this was rather by skin of teeth, and I don't really
understand how one should tune these values, so am asking the collective
wisdom of the SimH list for optimal parameters to SET XQ THROTTLE, or
alternative ways of ensuring a clean boot. Any ideas? An explanation of how
the throttle parameters are likely to interact with the VAXcluster
connection logic would help!

Or have I got hold of the wrong end of the stick - do these messages
indicate that the satellite is not waiting long enough for a response from
the boot server, and if so, do I need to be experimenting with CPU
throttling during this early boot phase?

Regards,
Paul.


KA655-B V5.3, VMB 2.7
Performing normal system tests.
40..39..38..37..36..35..34..33..32..31..30..29..28..27..26..25..
24..23..22..21..20..19..18..17..16..15..14..13..12..11..10..09..
08..07..06..05..04..03..
Tests completed.
>>>b xq
(BOOT/R5:0 XQ

  2..
-XQA0
  1..0..

%VAXcluster, system loaded from node HARDY1 (AA-00-04-00-01-04)
%VAXcluster, no connection to disk server
%VAXcluster, no connection to disk server
%VAXcluster, no connection to disk server
%VAXcluster, no connection to disk server
%VAXcluster, no connection to disk server
%VAXcluster, no connection to disk server
%VAXcluster, no connection to disk server
%VAXcluster, no connection to disk server
%VAXcluster, no connection to disk server
%VAXcluster, no connection to disk server
%VAXcluster, no connection to disk server
%VAXcluster, no connection to disk server
%VAXcluster, no connection to disk server
%VAXcluster, no connection to disk server
%VAXcluster, no connection to disk server
%VAXcluster, no connection to disk server
%VAXcluster, no connection to disk server
%VAXcluster, no connection to disk server
%VAXcluster, no connection to disk server
%VAXcluster, no connection to disk server
%VAXcluster, PE boot driver initialization failed, maximum retry limit
exceeded

%VAXcluster, boot driver unable to establish a virtual circuit
HALT instruction, PC: 00005368 (BRB 5367)
sim>

The HARDY3 instance of SimH is running a very recent version of SimH:
sim> sh ver
VAXStation 3900 (KA655) simulator V4.0-0 Beta
    Simulator Framework Capabilities:
        64b data
        64b addresses
        Threaded Ethernet Packet transports:PCAP:TAP:VDE: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: x86 (Release Build) on Feb 23 2018 at
22:13:52
        Memory Access: Little Endian
        Memory Pointer Size: 32 bits
        Large File (>2GB) support
        SDL Video support: SDL Version 2.0.5
        PCRE RegEx support for EXPECT commands
        OS clock resolution: 1ms
        Time taken by msleep(1): 1ms
        OS: Linux HardyWC1D 4.9.0-6-amd64 #1 SMP Debian 4.9.82-1+deb9u2
(2018-02-21) x86_64 GNU/Linux
        git commit id: e3543cbb

The relevant lines from the SimH ini file are:
;
; Attach Ethernet to a network interface
set xq mac=08-00-2B-AA-BB-CE
attach xq eth0
set xq throttle=on
set xq throttle=time=10;burst=2;delay=20
;
; Set SIMH options
set cpu idle
set cpu model=VAXstation

--
Paul  Hardy
web: www.paulhardy.net