[Info-vax] Reading Gordon Bell's VAX strategy document

[John Dallman]

Gordon Bell, who was Vice-President of Engineering at DEC 1972-83 is
still alive and documenting much of his life on the web. There's DEC
stuff at https://gordonbell.azurewebsites.net/Digital/DECMuseum.htm

Something particularly interesting is this document on DEC strategy as of
1979:

https://gordonbell.azurewebsites.net/Digital/VAX%20Strategy%20c1979.pdf

At the time, DEC's other active product ranges were PDP-8, DEC-10/DEC-20
and PDP-11. They had decided in 1975 to create an architecture that built
upwards from the PDP-11, rather than building lower-cost DEC-10 machines.
The reasons for doing that were the large installed base of PDP-11s and
the convenience of 8-bit bytes for data communications, especially with
IBM mainframes. 

As of 1978/70 they had achieved this and were deciding what to do next.
The strategy expressed in this document is to continue to sell the other
ranges, but concentrate development efforts on the VAX family, and that's
what basically happened. Using a single architecture is seen as a
competitive advantage against IBM's proliferation of incompatible
architectures, which is pretty reasonable, since IBM saw the same problem.


Bell regards competition from "zero cost" microprocessors such as the
8086 and 68000 as likely more significant than other minicomputer
companies, but fails to make a plan to deal with them. DEC was eventually
defeated by 80386 and later PCs and RISC workstations, and that failure
seems to start here. He assumes that DEC can dominate the market for
terminals for its minis by using PDP-11 and VAX microprocessors, but
doesn't seem to realise that compatible terminals can be built at much
lower cost using third-party microprocessors. In any case, the
replacement of minis by PCs and workstations meant that the terminal
market basically vanished. 

The idea of running VMS on a terminal with a total of 64KB of RAM and ROM
in 1982 seems implausible now, but it seems to have been the reason for
512-byte pages. Bell praises the extremely compact VAX instruction set
and its elaborate function calls, without appreciating the ways they will
come to inhibit pipelining and out-of-order execution, and thus doom the
architecture to uncompetitive performance. 

John