IBM PC Network

Lyle Bickley lbickley at
Sun May 23 14:18:58 CDT 2021

On Sat, 22 May 2021 23:00:31 -0600
Grant Taylor via cctalk <cctalk at> wrote:

> On 5/22/21 6:50 PM, Lyle Bickley via cctalk wrote:
> > Wow, never heard of "Tokenray" ;)  
> Nor have I.
> > BTW: 16 Mbit Token Ring was much more reliable (especially in "noisy" 
> > environments) and considerably faster with more consistent performance 
> > than 10 Mbit Ethernet.  
> I've heard tell that Token Ring worked MUCH better on extremely busy 
> networks.  Purportedly Ethernet starts having problems when there are 
> more and more systems and / or a higher and higher percentage of 
> utilization is happening.  I seem to remember that Ethernet had problems 
> starting about 80% utilization while Token Ring could easily handle 95% 
> utilization or higher.
> > plus IBM never upgraded Token Ring past 16 Mbit.  
> Sure they did.
> 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..."


"Note: IBM Statement of Direction, effective October 2001: For z900 server,
this feature is called the OSA-2 Token Ring feature, and can only be
configured as two 4/16 Mbps Token Ring ports. Note: Effective October 2001:
OSA-2 Token Ring feature (feature code 5201) is superseded by the OSA-Express
Fast Ethernet feature (feature code 2366), and OSA-Express Token Ring feature
(feature code 2367), as required. OSA-2 Token Ring feature (feature code 5201)
is not carried forward on G5/G6 server to z900 server upgrades."

To download the Redbook:

Interestingly, in spite of their statement of direction, for a time, IBM did
for a period make a "High-Speed 100/16/4 Token- Ring PCI Management Adapter" It
was NOT popular - and not many were sold. (For more detail, see:

Ethernet had "won" the hearts and minds of IT folks (plus Ethernet by that time
was full duplex - at both 100Mbps and 1000Mbps, potentially doubling it's
capabilities). Ethernet also could be implemented for a fraction of the price
of Token Ring. When IBM began to support Ethernet on mainframes, that was
the "death knell" of Token Ring ;)

As a networking company we never installed any 100Mbps Token Ring networks -
and weren't aware of any implemented by our competitors.

73   NM6Y
Bickley Consulting West

"Black holes are where God is dividing by zero"

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