[TUHS] Why did PDPs become so popular?

[Paul Winalski]

On 12/27/17, Dave Horsfall <dave at horsfall.org> wrote:
> On Wed, 27 Dec 2017, Dave Ritchie via TUHS wrote:
>
>> I think that steep educational discounts and equipment grants from
>> Digital to major collages also had a major impact, as did the existence
>> of DECUS that made a lot of software readily available.
>
> IBM practically gave away their kit to educational institutions too (and
> made their money from the maintenance); there was no way that the
> University of NSW e.g. could've afforded their 360/50 otherwise,

That may have been true in the 1960s, but by the mid-1970s IBM
System/360/370 was no longer competitive in the educational market.
Circa 1973, Boston College--a true Blue IBM shop with a
System/370-145--wanted to provide time-sharing services to the student
body.  For less than the cost to upgrade the model 145 to a 158, they
bought a PDP-11/70 and ran RSTS on it.  Similarly Holy Cross (my alma
mater) had outgrown their System/370-125 by 1976.  For the price of an
upgrade to a model 135, they could by a complete VAX-11/780 system for
academic use and retain the S/370-125 exclusively for college admin
purposes.  The 11/780 was equivalent in compute power and memory
capacity to a S/370-158, but for about 1/4 the cost.

-Paul W.