[AFMUG] Mikrotik x86 and ROS 6.x problems on 100M Ethernet links

[Ken Hohhof]

I recently upgraded one of those RouterMaxx 1106 routers from 5.2 to 6.33.1 
(I actually configured a new router and swapped hardware).  Ever since, I 
have had performance problems with a couple ports that are connected to 
radios with 100M Ethernet ports.  The most obvious symptom is that Winbox 
won't stay connected or can't download plugins, but I also see pings dropped 
even to the directly connected equipment.

I was a bad boy making multiple changes at once, so I've been gradually 
walking them back in the lab on the original router, I upgraded it to 6.33.1 
and the problem appeared.  I dropped back to 6.31 and it was still there, 
but when I dropped back to 5.26 everything was fine again.  I haven't tried 
earlier 6.x versions yet, 6.31 is the oldest x86 version I have handy.  This 
is not a radio problem, I can reproduce it with a directly connected laptop 
if I force the laptop NIC to 100M FDX.

Is anyone familiar with this problem?  I can't find anything on the Mikrotik 
forums.  I guess I can live with 5.26 if I have to, but I'd like to know 
what is causing this.  Do I just need to change some configuration 
parameter?  I know 6.x brought out hardware only queues, but I think that's 
for Routerboards, not x86.  Is there a problem with the Intel NIC drivers 
included with 6.x?  Any chance that an earlier or later version of 6.x will 
work for me?  I see nothing in the change logs about it.