IBM PC Network

Wayne S wayne.sudol at
Sun May 23 16:18:35 CDT 2021

ISTR That the 2 main issues hindering wide spread adoption of TR was cost and and not knowing where TR development was headed. 
The Type 1 cabling needed to each port on the hub was expensive vs thick/thin Ethernet with taps (as were the hubs). Also, there was no second source for TR chips so everyone who wanted to make TR hardware was at the mercy of the IBM chip pricing so there weren’t too many TR cards being manufactured by anyone other than IBM. I recall the Madge TR cards for IBM ps/2 machines being about $400 ea circa 1992.
So you had a lot of cost standing in the way if you were thinking about going/staying with TR and had hundreds of workstations.

As for development, there was an ethernet roadmap ( don’t remember the group that put it together) stating that 100 mbit was next running over shielded twisted pair then unshielded tp. And 1000 mbit was possible. 
For TR, No one knew if IBM would up the speed past 16 mb and allow TR chips to be made cheaply. 

Also the fact that token passing is inherently slower than CSMA/CD did not help to sell TR.
The analogy was that if you had a long street with many stop lights, using TR would be like having every light be red and having to stop at each light, where using Ethernet some of the lights would be green and no stop required.

IBM tried to use that to their advantage and use to say since the amount of time it takes to token pass could be measured precisely that the network response as a whole could be determined and capacity planning was more deterministic using TR than Ethernet.

My company was a big IBM shop and whatever IBM recommended we pretty much did. Used TR, and Banyon/Vines for networking to PCs. 

Sent from my iPhone

> On May 23, 2021, at 12:56, Paul Koning via cctalk <cctalk at> wrote:
>> On May 23, 2021, at 3:18 PM, Lyle Bickley via cctalk <cctalk at> wrote:
>>> On Sat, 22 May 2021 23:00:31 -0600
>>> Grant Taylor via cctalk <cctalk at> wrote:
>>> ...
>>> You can find commercial Token Ring cards that support, 4 Mbps, 16 Mbps, 
>>> /and/ *100* Mbps.  I see them on eBay monthly.
>>> I heard that IBM developed 1,000 Mbps / 1 Gbps Token Ring in the lab. 
>>> But that no commercial products were ever made.
>> Here's IBM's "Redbook" on Token Ring:
>> "IBM does not view high-speed Token Ring as a requirement for the majority of
>> its customers, and therefore the decision has been made not to provide 100
>> Mbps high-speed Token Ring uplinks on its products..."
> Interesting.  IBM also did quite a lot of work on FDDI, but that's a very different technology than 802.5 (and a better one in many ways).
>    paul

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