[Simh] simh on RaspBerry Pi

[Wilm Boerhout]

What he said :-)
Op ma 15 feb. 2016 om 20:47 schreef Thomas Merritt <simh at tj.merritts.org>

>
> > On Feb 15, 2016, at 8:37 AM, Johnny Billquist <bqt at softjar.se> wrote:
> >
> > On 2016-02-15 16:15, Paul Koning wrote:
> >>
> >>> On Feb 15, 2016, at 9:01 AM, Wilm Boerhout <wboerhout at gmail.com>
> wrote:
> >>>
> >>> Will Senn schreef op 15-2-2016 om 14:26
> >>>
> >>> [snip]
> >>>
> >>>> Are you documenting the setup process for your endeavors, or just
> blogging about the result? I think it would be interesting to see how you
> clustered those Pi Vaxen as much as to know it was possible. I've got a few
> Pi around looking for something to cluster around...
> >>> There are three parts to a successful setup:
> >>>
> >>> 1. Since each Pi has only one Ethernet interface, make sure you use a
> >>>   wired connection (wireless isn't real Ethernet)
> >>
> >> Well, Wireless is 802.11 which indeed isn't 802.3 / Ethernet.  But
> that's not really relevant.  The question is whether it uses Ethernet
> addressing and offers an Ethernet-compatible MAC layer API, and 802.11
> certainly does.  You can run SimH Ethernet just fine over a wireless LAN.
> I've run PDP11 SimH that way with no problems.
> >
> > Actually, I have run into problems. The broadcast domain, as well as the
> Unicast have slight differences to Ethernet, which makes it sometimes fail
> in subtle ways.
> > Having a second mac address on a WiFi interface, one that is used by
> simh, though tun/tap, does not work that well with WiFi. Unfortunately.
> >
> > I've definitely had problems keeping it working under OS X at least. And
> I'm pretty sure I've read of others having the same problem.
> >
> >       Johnny
> >
> >
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>
> This is a feature of 802.11.  The packet format over the air for 802.11
> has two MAC addresses in it to in theory enable bridging.  One for the
> radio and one for the sender.  Most 802.11 firmware just stuffs the radio's
> MAC address in both and ignores the MAC address in the original frame when
> sending, and when receiving the senders radio MAC address is used in the
> frame propagated to the computer by the adapter.  The result is that
> everything is sent as if from the host and not the VM and replies are
> delivered back to the host and not the VM.  This can be worked around in
> the hypervisor as VirtualBox does for IPv4 and to some degree IPv6.  But
> don't expect a SimH machines to be able to communicate over WiFi without a
> lot of work in SimH’s networking implementation.
>
> -- TJ
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