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The information on Groklaw is not intended to constitute legal advice. While Mark is a lawyer and he has asked other lawyers and law students to contribute articles, all of these articles are offered to help educate, not to provide specific legal advice. They are not your lawyers.

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Version 6 I believe | 198 comments | Create New Account

Comments belong to whoever posts them. Please notify us of inappropriate comments.

Version 6 I believe

Authored by: DieterWasDriving on Wednesday, October 24 2012 @ 06:58 PM EDT

Not quite right on the history.

Original Ethernet ran at 3Mbps. That rate was chosen because the processor
microcode and data bus could transfer data a bit faster, avoiding the need for a
full-packet buffer.

The maximum packet size was chosen so that an 12 bit counter could detect an
overrun or babbling transmitter with a NAND gate on the two high bits. That was
effectively an 11 bit counter on the 6MHz decoder clock.

In that initial implementation, the processor actually generated the 8 byte
preamble as part of the frame data. The CRC was generated by hardware, but was
read out and appended to the frame by the processor.

Some of the early Ethernet implementation were surprisingly crappy. The 3c501
was one of the earliest adapters, with the major feature of having a 2KB RAM
chip so that it could hold an entire frame. But, like other contemporary
implementation, once a frame to be transmitted was loaded into RAM, it lost the
ability to receive inbound frame.

[ Reply to This | Parent | # ]

Version 6 I believe - Authored by: JamesK on Wednesday, October 24 2012 @ 10:03 PM EDT

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