IBM PC Network

dave.g4ugm at dave.g4ugm at
Sun May 23 04:49:01 CDT 2021

> -----Original Message-----
> From: cctalk <cctalk-bounces at> On Behalf Of Jim Brain via
> cctalk
> Sent: 23 May 2021 08:03
> To: cctalk at
> Subject: Re: IBM PC Network
> On 5/23/2021 12:31 AM, Grant Taylor via cctalk wrote:
> > On 5/22/21 7:12 PM, Jim Brain via cctalk wrote:
> >> I guess that's a selling point of TR, but I loathed it when
> >> introduced to it after using Ethernet at UIUC.  Having to learn
> >> CPI-C, LU-2, LU-6.2, APPC, etc. and configure Communications
> >> Manager/2 on OS/2 to emulate a FEP (3174?, not sure, my mind tended
> >> to bury such information, and in fact I'm not sure if that's what it
> >> did or if it connected to a FEP, that info is gone and I've no desire
> >> to go review it).
> >
> > Given the things that I play with, I'd like to know more.  But I
> > suspect that this isn't the forum.
> Oh, I don't know, I mean, CM ES and CM/2 were just OS/2 emulators of a
> FEP, I believe (they were emulating something, I know that much), and we
> talk about other emulators on here all the time.

I don't believe that any of the early LAN products emulated what IBMers would call an FEP.  
Generally, an FEP is a 37XX computer running NCP, EP or PEP.

Originally these had an interface to the channel and serial interfaces to which a variety of devices could be connected, so simple async terminals, terminal cluster controllers and RJE workstations.
There were also "remote" FEPs that connected to a local FEP via a comms line. Later Token Ring and Ethernet interfaces were added. IBM did produce an emulation of the 37xx boxes as

but this runs on the mainframe.
The early tools generally appeared to the Mainframe as a 3174 Terminal Cluster Controller and attached screen. They did not emulate any of the 37xx or 3174 CPUs, they "just" re-implemented the IBM protocols.
So you still (usually) needed an FEP on the mainframe although it was also possible to use a Token Ring interface on a channel attached 3174 (3174s could be directly attached to the mainframe) or even attach to the channel using PC channel cards. 
The tools were not limited to terminal emulation, they would also allow PC applications to connect to the Mainframe using a range of SNA protocols.
I would say they are all old enough and obsolete enough to be considered "in scope" on here.


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