Subject: http://www.fefe.de/linuxeth/
Date: 15 Feb 2001 08:09:37 +0100


Add something like that:

Don't buy a card with RealTek Chipset. A comment in the FreeBSD
driver sumarizes why they are slow:
http://www.FreeBSD.org/cgi/cvsweb.cgi/src/sys/pci/if_rl.c?rev=1.56&content-type=text/x-cvsweb-markup&only_with_tag=HEAD

   The RealTek 8139 PCI NIC redefines the meaning of 'low end.'
   This is probably the worst PCI ethernet controller ever made,
   with the possible exception of the FEAST chip made by SMC. The
   8139 supports bus-master DMA, but it has a terrible interface
   that nullifies any performance gains that bus-master DMA
   usually offers.
 
   For transmission, the chip offers a series of four TX
   descriptor registers. Each transmit frame must be in a
   contiguous buffer, aligned on a longword (32-bit)
   boundary. This means we almost always have to do mbuf copies
   in order to transmit a frame, except in the unlikely case
   where a) the packet fits into a single mbuf, and b) the packet
   is 32-bit aligned within the mbuf's data area. The presence of
   only four descriptor registers means that we can never have
   more than four packets queued for transmission at any one
   time.
 
   Reception is not much better. The driver has to allocate a
   single large buffer area (up to 64K in size) into which the
   chip will DMA received frames. Because we don't know where
   within this region received packets will begin or end, we have
   no choice but to copy data from the buffer area into mbufs in
   order to pass the packets up to the higher protocol levels.
 
   It's impossible given this rotten design to really achieve
   decent performance at 100Mbps, unless you happen to have a
   400Mhz PII or some equally overmuscled CPU to drive it.

You may say that you don't care about preformance and RealTeks
are really cheap and in many stores the only NICs you can
get. Still don't buy them. They often just don't work and you
spent to much time debugging obscure failures. For example
RealTeks tend to change their MAC-Address wihtout motivation. I
know a company which bought 100 RealTeks a year ago - they had to
trash arround 50 up to now because there where broken.

Save you hassles - don't buy a RealTek.

doobee