[MontelLUG] [OT] Commenti alle schede di rete

[Samuele]

Dall'altra parte si parlava di driver wifi... mi sono venuti in mente 
alcuni commenti presenti all'interno del driver delle schede realtek 
(che potete trovare online).
Ricordo che c'era un sito che contava le parolacce all'interno del 
kernel linux con tanto di grafico.

  * 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...

[cut]

  * 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.

/*
  * Here's a totally undocumented fact for you. When the
  * RealTek chip is in the process of copying a packet into
  * RAM for you, the length will be 0xfff0. If you spot a
  * packet header with this value, you need to stop. The
  * datasheet makes absolutely no mention of this and
  * RealTek should be shot for this.
  */