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It turned out that a manufacturer of Ethernet interface parts had made a mistake in the hardware state machine that controlled the transmitter. It wasn't 3Com,

It turned out that a manufacturer of Ethernet interface parts had made a mistake in the hardware state machine that controlled the transmitter. It wasn't 3Com, was it? The irony of that could make people's heads explode!

Animats 7y ago
No, a lower-level part. Can't find the obscure paper where that was written up. Coax Ethernet also suffered from basic electrical problems. It had a signal down to DC, so you couldn't decouple cable sections with a capacitor, like you can with cable TV coax. No problem in a room, but inter-building cable runs had grounding issues. The outside of most coax connectors is treated as a ground and bolted to the enclosure, but you can't do that with long runs of Ethernet. Ethernet cables evolved to have both sides isolated from ground, with special insulated connectors, but you had to ground somewhere for safety. Signal loss was also a problem. The receiver must be able to detect a collision from the furthest node while the local node is sending. So the amount of loss allowed end to end is quite low. Thus the need for huge RG-8 coax and huge SO-239 coax connectors. At the time, I was working at an aerospace company which built RF gear to communicate with satellites, and we had RF experts around. They were not impressed with Ethernet as a transmission system. They wanted something more like cable TV, with an RF carrier and multiple channels, which is what Internet via coax from cable TV vendors is now. With that, you can run miles of cable, put in booster amps, have lightning arrestors, and deal effectively with the real-world problems of outside plant. Coax Ethernet was a minimum viable product. Good concept, but needed a complete electrical redesign to scale. Ethernet over unshielded twisted pair ("10baseT" and up) is nice electrically. The cable is cheap and small. It's a differential signal, so it has good noise immunity to other signals and induced currents from power cables. 100m long runs of cable work. You need hubs and repeaters to go further. Those are tiny now, with custom silicon, but the first Ethernet repeaters for coax Ethernet were about a cubic foot of electronics. 1970s electronics needed a lot of parts to do anything.

Animats 7y ago

No, a lower-level part. Can't find the obscure paper where that was written up. Coax Ethernet also suffered from basic electrical problems. It had a signal down to DC, so you couldn't decouple cable sections with a capacitor, like you can with cable TV coax. No problem in a room, but inter-building cable runs had grounding issues. The outside of most coax connectors is treated as a ground and bolted to the enclosure, but you can't do that with long runs of Ethernet. Ethernet cables evolved to have both sides isolated from ground, with special insulated connectors, but you had to ground somewhere for safety. Signal loss was also a problem. The receiver must be able to detect a collision from the furthest node while the local node is sending. So the amount of loss allowed end to end is quite low. Thus the need for huge RG-8 coax and huge SO-239 coax connectors. At the time, I was working at an aerospace company which built RF gear to communicate with satellites, and we had RF experts around. They were not impressed with Ethernet as a transmission system. They wanted something more like cable TV, with an RF carrier and multiple channels, which is what Internet via coax from cable TV vendors is now. With that, you can run miles of cable, put in booster amps, have lightning arrestors, and deal effectively with the real-world problems of outside plant. Coax Ethernet was a minimum viable product. Good concept, but needed a complete electrical redesign to scale. Ethernet over unshielded twisted pair ("10baseT" and up) is nice electrically. The cable is cheap and small. It's a differential signal, so it has good noise immunity to other signals and induced currents from power cables. 100m long runs of cable work. You need hubs and repeaters to go further. Those are tiny now, with custom silicon, but the first Ethernet repeaters for coax Ethernet were about a cubic foot of electronics. 1970s electronics needed a lot of parts to do anything.