fxp0: device timeout

My server in the attic was recently reinstalled from scratch with
FreeBSD 5.stable (actually: RC2, and now upgraded to 5-stable), see the
attached dmesg.boot for the dmesg info.

This machine in the exact hardware configuration was running fine in its
6-current days. The reason for 'down'grading was the fact that overtime
it seems that a subtle filesystem problem arose, that lead to random
crashes (well, random... take a lot of vm activity and at some point
vnlru would lead to a kernel panic), but the network was perfectly fine.

Now, with the 5.x install, I have regular problems with fxp0.

In /var/log/messages and dmesg I get this:
(The last line comes from ifconfig fxp0 link0, which I added yesterday
to see if it would solve problems, the same symptoms occur without that
option)

Apr 25 18:15:08 eeyore kernel: fxp0: device timeout
Apr 25 18:15:08 eeyore kernel: fxp0: Microcode loaded, int_delay: 1000 usec  bundle_max: 0

The symptoms:
* network freezes for 30 seconds or something like that, after a while
pings start to work again and everything moves on.

When:
* combinations of network activity and/or disk activity. Starting bacula
will guarantee device timeouts, as will browsing from a workstation combined
with e.g. using a samba share

The interface:

fxp0: <Intel 82558 Pro/100 Ethernet> port 0xe000-0xe01f mem 0xe3000000-0xe30fffff,0xe3101000-0xe3101fff irq 5 at device 17.0 on pci0
miibus1: <MII bus> on fxp0

fxp0: flags=9843<UP,BROADCAST,RUNNING,SIMPLEX,LINK0,MULTICAST> mtu 1500
	options=8<VLAN_MTU>
	inet6 fe80::208:c7ff:fe25:7560%fxp0 prefixlen 64 scopeid 0x2 
	ether 00:50:da:3d:d7:f6
	media: Ethernet autoselect (100baseTX <full-duplex>)
	status: active

There are 2 'special' things with this interface:
* the mac address is changed from /etc/start_if.fxp0
* it is used with VLAN's (802.1q tagging)

I looked in the mail archives, and of course it is clearly an interrupt
problem. I did the usual stuff: put the card in different PCI slots,
force it to different IRQ in the BIOS, but still no improvement.
Furthermore I don't believe that hardware should change that much just
by reinstalling FreeBSD, so I tend to believe that something is
different between 5.x and 6.x.

Does anyone recognize these symptoms and have a nice solution for me?
Or if people decide I should PR this: what kind of info would make
debugging easy? vmstat 1 info would take a little work to collect for
these kind of outages, but I can do some scripting to fix that of course
:-)

Greetings,

Mark
-- 
Nice testing in little China...