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Gigabit Ethernet: On-Board Chips Reviewed

Who Needs Gigabit Ethernet?

During almost any discussion about Gigabit Ethernet, someone almost inevitably claims that the technology is unnecessary. But does this argument have any merit? The 100 MBit/s, 100BaseT-Ethernet standard offers a theoretical maximum data transfer rate of 12.5 MBytes/s (MB/s). In real world applications, the actual rate is usually 8 MB/s. In everyday operations, such as drag-and-drop-based file transfer, this rate is usually just good enough to download even large files from the network server, although there is a wait involved.

However - and that is a big however - 8 MB/s, represents a tight bottleneck for many applications. For example, hard drives often allow for up to 60 MB/s and a modern DVD drive offers more than 10 MB/s. Thus, 100BaseT-Ethernet's data transfer rate of 8 MB/s pales in comparison to that of a DVD player or hard drive. The disparaty becomes apparent while playing a game or watching a DVD that is housed on another PC's hard drive in a network.

But almost like magic, adding Gigabit Ethernet eliminates many of these bottlenecks. While DVD players, hard drives and other media cannot accommodate maximum throughput, they can accommodate up to five times the data tranfer rate compared to what 100 Mbit, 100BaseT-Ethernet offers.

Ironically, many users who pay a lot of attention to paying extra for the fastest CPUs, next-generation DRAM or the fastest hard drives are not bothered as much by slow network data tranfer performance. These are the users who often claim that Gigabit Ethernet is not necessary. However, the argument over whether Gigabit Ethernet is really necessary or not is moot, as Gigabit Ethernet has already become ubiquitious and affordable, while enabling PCs to share data across across several platforms as if the data were stored locally.

How Does Gigabit Over Copper Work?

The 100BaseT protocol operates with two pairs of 100 MHz veins in a cable screened in pairs and with a total of eight veins. In comparison, the Gigabit Ethernet alias 1000BaseT occupies all lines. However, during full-duplex operations, the cables would need to handle 250 MHz, which is often not the case with many cables sold in retail channels.

Echo Cancellation is the solution. In other words, a pulse amplitude modulation and an equalization of the jitter effects are occurring. During full-duplex operations, the signals of sender and receiver overlap. To ensure a good reception, the own signal is subtracted from the receiving signal on the other end (Echo Cancellation) - of course, all this with major support from the system processor. Pulse amplitude modulation only describes the stronger type of pulse amplitude, while the occurring distortions (jitter) have to be countered actively (e.g., by calculating approximate values).