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First Gigabit Ethernet Chip Demo
An anonymous reader writes "Broadcom demonstrated the
world's first Gigabit Ethernet transceiver chip for
existing CAT5 copper cabling yesterday at
NetWorld+InterOp '99. Packaged in a 256-pin TBGA, Broadcom
has begun delivering initial samples at $75/chip. No word on
when full production starts or
when to expect hubs, switches, or NICs based on the chip."
Of course, >99% of Gigabit Ethernet is full-duplex so there are no collisions. This is partly because, up until now, all GigE was fiber-based, and most fiber topologies have one strand for transmit, one for receive (i.e. no way to collide). If you did build half-duplex, I believe the collision domain would be like 20 meters, not very useful.
:-)
The reason Broadcom's chip is so complicated is that for full-duplex GigE on copper, all 4 pairs in the cable are used, _in both directions_. This means the chip uses fancy DSP techniques to subtract what is transmitting from what is receiving. It handles FEXT and NEXT (far-end and near-end cross-talk) as well.
The only other concern is that the end-station just cannot create frames fast enough @ 1518 bytes, so there is a proposal for jumbo frames to enable endstations to lower their rate of frame generation. Still, for decent TCP stacks you can see 500-800 Mbps right now, which is a good bit better than 100Mbps.
The ATM fixed-53B cell is an interesting idea, since it allows for uniform memory allocation per cell (versus ethernet, where you don't know if you need 64 or all the way up to 1518), but in hardware, often the implementation for Ethernet is to use linked-lists of buffers (say of 128B) which will have good efficiency.
Problems like these can always be solved, and Ethernet is cheap and standard.
Death to ATM!