Delete comment from: Ken Shirriff's blog
>> what differs between 3Mbps and the first 10Mbps ethernet.
3MB Ethernet had 8bit source and destination addresses, I think a 16bit CRC and a different preamble length. There was a hint that Intel's first ethernet controller (i82586) was configurable enough to implement 3MB Enet, but I don't think anyone tried very hard to actually make it work. By that time, 3MB was clearly "legacy", and the interfaces that existed (Stanford/Xerox/cisco Multibus, Unibus, and Massbus) were "enough" for the small groups that required them.
As another reference for PUP implementation, I think you should be able to find the Stanford TOPS20 source code (in PDP10 assembler) online. (if not, I could upload it.) Stanford was using PUP for remote terminal access well into the mid-1980s.
Jan 23, 2018, 2:35:25 AM
Posted to Xerox Alto's 3 Mb/s Ethernet: Building a gateway with a BeagleBone