Re: The Design of Design

According to MitchAlsup1 <mitchalsup@aol.com>:

S/360 invented eight bit byte addressed memory with larger power of 2
data sizes, which I think all by itself is enough to explain why it
survived. All the others, which were word or maybe decimal digit
addressed, died. Its addresses could handle 16MB which without too
many contortions was expanded to 2GB, a lot more than any other design
of the era. We all know that the thing that kills architectures is
running out of address space.

>
Note to self:: when designing a 36-bit machine, do not cripple it
with 18-bit addresses with inherent indirection....

In fairness, in 1963 when the PDP-6 was designed, 256K words seemed
like an enormous amount of memory. A 7094 could only address 32K. Even
with that limit, PDP-10 series lasted until 1983. Twenty years was a
pretty good run.

When it was new, S/360 was considered a memory hog. When they realized
that OS/360 needed 64K to run and a lot more to run well, they quickly
came up with DOS and TOS that ran in 16K and a minimal BOS that ran in
8K. In retrospect we know that memory prices dropped quickly and the
big address space was a good idea, but it was a gamble at the time.
--
Regards,
John Levine, johnl@taugh.com, Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail. https://jl.ly