Ein wahrer Kommentar im FreeBSD-Treiber für den ganzen Realtek-Scheiß, den Otto-Normalbenutzer sich im Mediamarkt unter dem Zeichen von „Geiz ist geil“ als Netzwerkkarte verkaufen lässt:
* 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
* 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.