Microsoft-Paul Allen

[Paul Koning]

> On Oct 19, 2018, at 1:14 PM, Al Kossow via cctalk <cctalk at classiccmp.org> wrote:
> 
> 
> 
> 
>>> IBM developed a Token Ring card for the PC in time for its launch
> 
> IBM's initial networking for the PC (The PC Network) was broadband, based
> on technology from Sytek. 4Mb token ring was released later. Exact dates
> are in the manuals on bitsavers.
> 
> http://bitsavers.org/pdf/ibm/pc/pc_network/6322916_PC_Network_Technical_Reference_Sep84.pdf

That's basically Ethernet except very slow (2 Mb/s, even slower than "Experimental Ethernet").  But it's described as CSMA/CD, and it uses the much-cursed Intel 82586 Ethernet chip.

Token ring ended up a failure because it was slow and completely incompatible with other 802 networks, from the backward addresses to the bizarre pseudo-multicast scheme to the source routing bridges.  In spite of IBM marketing claims, 802.5 data link layer is not a well behaved design.  Later token rings, like FDDI, used the 802.4 token passing algorithm ("Timed token"), avoiding the 802.5 algorithms completely.

	paul