[Simh] VAX/VMS

[Clem Cole]

On Tue, Feb 16, 2016 at 9:56 AM, Timothe Litt <litt at ieee.org> wrote:

> Nonetheless, Brooks (@IBM) definitely gets credit for the first
> ​ ​
> commercial line of architecturally (forward) compatible machines.  Prior
> ​ ​
> to that inspiration, every new machine was unique and most software
> started over (including compilers).
>

​Amen -- I credit ​

​Brooks for 3 things good things and one bad

Good:
1.) architectural compatibility
2.) ​a 32 bit word size with an large address space (24 bits in this case)
3.) 8 bit byte

Bad:
      EBCDIC over ASCII

I used to work with the Chief Designer of Model 50 at one of my start ups.
He had some very interesting stories.   Gordon Bell always said the single
worst mistake you can make in an architecture is too few address bits.
 Russ said that the word and bytes sizes that Brooks wanted, Amdahl thought
were "wasteful and frivolous" but Brooks one the war.     Supposedly Amdahl
wanted a 6 bit byte, but Brooks was said to thrown him out of office until
he came back with something that was a power of two "that he could
program."

FWIW:  Around the same time, Seymour Cray would use a 6 bit byte at CDC and
not embrace 8 bits until the Cray-1 10 years later --- and look at the
craziness that their systems had to handle with N different codes - you
actually see some of impact in design of Pascal by Wirth years later.


The using
EBCDIC
​instead of​
 ASCII
​ was a sad thing.   IBM had been heavy in development of ASCII and I
believe even chaired the ANSI committee creating it.   In fact if you look
at marketing literature, S360 was supposed to be the
first commercial system to support it.   But with OS/360 being so late,
Brooks was said to make the decision to keep the primary code EBCDIC (for
compatibility).   Until the switch to Power years 25+ years later, IBM (and
its users) would pay that price.

​Clem​
​
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.trailing-edge.com/pipermail/simh/attachments/20160216/4ee0f424/attachment.html>