[tulip-bug] Capture Effect

[John William]

>From: Donald Becker <becker@scyld.com>
>To: John William <jw2357@hotmail.com>
>CC: tulip-bug@scyld.com
>Subject: Re: [tulip-bug] Capture Effect
>Date: Wed, 4 Oct 2000 00:33:47 -0400 (EDT)
<snip>
>Which FA301TX card?  (Yes, there are several substantially different
>versions).

Hardware revision D1, reports itself as:

00:0e.0 Ethernet controller: Lite-On Communications Inc LNE100TX (rev 21)
        Subsystem: Netgear FA310TX

according to "lspci -vv".

>I'm guessing that you have a PNIC-I chip.

I'm sorry - I don't know what version of the PNIC chip it has. Is there 
enough information in the card revision and PCI reporting to determine it?

>It appears that the PNIC-I is pretty picky about PCI bus timing.  Here is
>what we think is happening: On some systems, with some slightly out-of-spec
>PCI timing, the PNIC-I has a problem with receive FIFO synchronization.
>This causes some receive packets to be corrupted and thus dropped.
>
>The identical software load, adapter and network connection will work
>without error on another motherboard.
>
>The BSD driver has a work-around, but attempting to recover data from a
>known-corrupted packet is pretty much like trying to save the food from a
>broken glass jar.

Ok. That sounds like a reasonable explanation for why the card performs so 
poorly on receive (and would explain the framing errors). I'd say it's more 
than "some" however, under very heavy load, >90% of all packets are lost.

But if this is the case (implying a hardware problem with the card), why 
does it work normally on Win98 on the same machine? Same card, same 
motherboard, same everything - different OS.

>It might be easy for you to reproduce, but it's not easy to reproduce in
>general.  Swap out your motherboard, leaving everything else the same, and
>the problem will disappear.  These types of errors are very frustrating to
>track down precisely.

If you're suggesting "buy a new computer and the problem will go away"... 
well that is a solution, but not a reasonable one. This is a HP system 
(custom MB) so even if I were willing to invest in a new motherboard that 
wouldn't be an option. Besides, replacing a $20 networking card would be 
much easier than replacing a $200 MB.

I agree this problem is very frustrating to track down. It took long enough 
just to notice that the thing slows down dramatically under heavy network 
load (but not light load). I should just pull the FA310TX and put in a 
3C905C but I would really like to get this thing working correctly as we 
have more than a few of these cards.

- Bill

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