[Fwd: Slow Tx on SMC1211TX]

Hugh Fader hfader@ameritech.net
Sat Apr 10 17:53:23 1999

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More data on this problem: I discovered if I lower the MTU setting on
the ethernet interface that it dramatically increases the transmit rate.
I have lowered it from the default of 1500 to 1000. This decreases the
receive speed and increases the transmit speed. My understanding of MTU
is that it is the maximum packet size on the interface. I don't
understand why this would increase transmit speed though.

I am now getting Oversize ethernet frame messages which eventually seems
to shut down the interface, so lowering MTU is only a clue not a fix. I
notice that you have TX_BUF_SIZE in the driver being related to MTU
size. Is this something I should tweak?


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Message-ID: <370D5C25.8AB8C77A@ameritech.net>
Date: Sat Apr 10 17:53:23 1999
From: Hugh Fader <hfader@ameritech.net>
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To: linux-realtek@beowulf.gsfc.nasa.gov
Subject: Slow Tx on SMC1211TX
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Oops! I just sent this note to Becker and then saw on your web site you
want problem reports to go to linux-realtek. Sorry -- here's my message

Mr. Becker,

I am having some trouble with my SMC1211TX board and am hoping you can
help out. I have a network of 1 Linux box and 2 Windows 95 boxes. The
Linux box receives data at ~280 kbyte/sec but transmits at only 6
kbyte/sec. I am measuring this using smbclient from Linux to the Win95
machines and also using ftp from the Win95 machines to Linux. The Win95
machines seem to both transmit and receive at an acceptable rate between

each other using drag and drops of files.

Here are the details of the Linux box:
rtl8139.c v 1.06
Linux 2.0.36
Intel 233 MMX
Amptron TX3 motherboard
16 MB memory

All 3 machines are running SMC 1211TX boards. I just switched
motherboards from a very old P75 which was experiencing Rx overruns but
which seemed to transmit and receive at a fast rate. This leads me to
believe there is something about the TX3 motherboard that is causing
this problem. Can you give me any clues as to why the transmits would be

so slow?

Thanks in advance for any help and thanks for all the great work on the
network drivers.

Hugh Fader


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