> Given the little literature I've seen on the subject, and also the > amount of real-time control computers that I've seen in labs being > dismantled... I'd say that it was probably a late IBM response to PDP-11 > and HP 21xx and 1xxx process control computers.
That would be correct - and is even shown in the period advertisements from IBM. In keeping with the DEC philosophy, the S/1 was a very open system,and in the mid 1970s, IBM tried to cultivate a sea of third party vendors, as there was for other minicomputer makers at the time. Some ventured in, but the third party market really never grew much. The S/1 was not IBMs first minicomputer by any metric. In process control, for example, the System/7 predated the Series/I, and the 1800 family before that, and the 1710 before that. A System/360 could also do realtime process control using something called a 1070, but very few were used this way. -- Will