[COFF] What Happened to Interdata?

[Paul Winalski]

On 7/25/23, segaloco via COFF <coff at tuhs.org> wrote:
> Were Interdata machines
> problematic in some sort of way, or was it merely fate, with more popular
> minis from DEC simply spacing them out of the market?

I suspect that Interdata had the same problem with their S/360
lookalikes that RCA did with theirs.  If your business model is to
provide a cheaper hardware alternative to IBM, your machine has to run
IBM software, particularly the OS.  When IBM did their pre-release of
the S/370 specifications they deliberately left out key bits of the
privileged architecture, such as the detailed bit layout of the PSW.
Companies such as RCA and Interdata had make guesses while designing
their S/370 lookalikes and in some cases they guessed wrong.  RCA's
Spectra 70 couldn't run IBM OS/VS or DOS/VS and that made it a total
non-starter for most IBM commercial shops.  I suspect Interdata ran
into the same problem.  Yes, they could design their own me-too
operating systems, but they would always lag behind on new IBM OS
features, on which critical IBM applications would depend.  The IBM
customer base knew this and stuck with genuine IBM.  A lower price
point wasn't enough to make up for the incompatibility.

The advent of 32-bit minicomputers at the end of the 1970s brought
down for good the IBM price umbrella under which Interdata and other
lookalikes had been living.  An example of how high that price
umbrella had been:  In 1978 my undergraduate alma mater was a
true-blue IBM shop with a S/370 model 125 running batch, CICS, and a
small BASIC timesharing system for the students.  They'd outgrown the
model 125.  IBM's solution was to upgrade to a model 135.  For the
same price as the IBM processor upgrade, DEC was offering a complete
VAX-11/780 system to run timesharing and other academic computing,
with the S/370-125 devoted exclusively to the business side of things.
The 11/780 was roughly equivalent in computing power to an IBM
S/370-158--two models up from the 125.  Buying the 11/780 was a
complete no-brainer.

IBM was forced to cut prices on the S/370 line, and that fatally
destroyed Interdata's one advantage over true S/360/370.

-Paul W.