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| Authored by: JamesK on Wednesday, October 24 2012 @ 10:03 PM EDT |
Typo on my part. Actual speed 2.94 Mb/s.
{
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.
}
From the book: "Ethernet the Definitive Guide", by Charles E.
Spurgeon
"The signal clock for the experimental Ethernet interface was derived from
the Alto's system clock, which resulted in a data transmission rate on the
experimental Ethernet of 2.94 Mb/s."
The author worked on that 2.94 Mb LAN.
{
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.
}
One consideration for frame size is the risk of corruption of larger frames.
Another factor is the length/type field, which requires length values to be
below 1536. Otherwise it's considered to be a type field.
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