I am having quite some trouble getting the full speed out of 2 onboard Intel
82541GI gigabit cards (more detail below). The cards are able to receive 
data with
full speed (~100MB/s) but are only able to send at about half of that
(~50MB/s).

netio results to show what i mean:
Test PC1 = client / Problem PC = server
Packet size  1k bytes:  100440 KByte/s Tx,  50575 KByte/s Rx.
Packet size  2k bytes:  95284 KByte/s Tx,  49283 KByte/s Rx.
Packet size  4k bytes:  95811 KByte/s Tx,  50648 KByte/s Rx.
Packet size  8k bytes:  99554 KByte/s Tx,  50719 KByte/s Rx.
Packet size 16k bytes:  94888 KByte/s Tx,  50741 KByte/s Rx.
Packet size 32k bytes:  94797 KByte/s Tx,  50794 KByte/s Rx.

how it should be:
Test PC1 = client / Problem PC (using a NetXtreme Gigabit card instead 
of the
onboard network) = server
Packet size  1k bytes     102206 KByte/s Tx       93615 KByte/s Rx.
Packet size  2k bytes     114040 KByte/s Tx       101264 KByte/s Rx.
Packet size  4k bytes     114069 KByte/s Tx       106685 KByte/s Rx.
Packet size  8k bytes     114091 KByte/s Tx       114272 KByte/s Rx.
Packet size 16k bytes     114133 KByte/s Tx       114216 KByte/s Rx.
Packet size 32k bytes     114087 KByte/s Tx       114252 KByte/s Rx.

Problem PC:
Mainboard: Broadcom HT 1000 (Tyan S3970)
CPU: 2x Dual Core AMD Opteron 2210 (1800Mhz)
Chipset: Broadcom BCM5785
NET: Intel Corporation 82541GI Gigabit Ethernet Controller (onboard)
net module: e1000 (tested with 7.3.20 [from the kernel] and 8.0.6 
[downloaded from
the intel homepage])
Test OS #1: Suse 11.0 / kernel 2.6.25.18
Test OS #2: Gentoo / kernel 2.6.27.7
Test OS #3: Gentoo / kernel 2.6.18 (XEN dom0)

Test PC1:
CPU: 2x Pentium III (1000Mhz)
Chipset: Broadcom OSB4
NET: Broadcom Corporation NetXtreme BCM5701 Gigabit Ethernet (not onboard)
net module: tg3 (version: 3.94)
Test OS #1: Suse 11.0 /kernel 2.6.25.18
Test OS #2: Gentoo / kernel 2.6.27.7

Test PC2:
Chipset: ATI Technologies Inc SB700/SB800
NET: Intel Corporation 82571EB Gigabit Ethernet Controller (onboard)
net module: e1000 (version: 7.3.20)
Test OS: Gentoo / kernel 2.6.18 (XEN dom0)

Tests with the Problem PC and any of the Test PCs always gave the same
results (Only sending with ~50% of the speed its receiving.) Tests were made
with netio, iperf, copying a file via scp, copying a file via
nfsmounts/aoeexports/mounted iscsi-targets and hdparm/dd tests with aoe 
exports/iscsi
targets.
According to ethtool the cards are running with 1000 Mbps Full Duplex.

If i put one of the NetXtreme Gigabit Cards into the Problem PC i am 
able to get full
speed in both directions with every Test PC (as seen in the netio example
above).

Changing MTU to 9000 increased both sending and receiving by about 
10MB/s but
the sending speed was still only around ~50% of the receiving speed. Trying
different sysctl settings for net.* didn't help either. I also tried 
various Interrupt
handling settings of the driver but no matter what i changed, sending 
speed was still slow.
Tests were made with the PCs connected via a Gigabit Switch and also with a
crossover gigabit cable.

Is there anything else that i could test? Because right now i am out of 
ideas and am starting to
think that its either a driver problem or the cards are simply broken.


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