🚀 go-pugleaf

John Levine <jo...@taugh.com> wrote:
> In article <5b71ce88...@news.dslextreme.com> you write:
>> Your so-called "categories" are arbitrary and mostly meaningless.  Even before
>> the advent of the 360, they were always "general purpose" computers.  Meaning
>> they could be used for any application, given the proper programming.  The
>> salient differences were in CPU speed, storage capacity, and data transfer
>> rates. ...
> 
> Yes and no.  The architecture of the binary word addressed 704x/709x
> scientific machines was rather different from the decimal word 7070 or
> the character addressed 705/7080.  Sure, they were all Turing
> complete, but the 7080 was bad at floating point arithmetic and the
> 7090 was bad at moving character strings around.
> 
> We all think it's obvious to have byte/word addressing where the word
> addresses are byte addresses with the low bits zero, but it wasn't
> obvious at all before IBM invented it for the 360.  Once they had a
> memory architecture that could work either way, building the
> instruction set wasn't so hard.

Or maybe not so obvious. With word addresses you can address a lot more
memory with a given-length address field. A lot of machines, like the
PDP-10, solved this problem by having byte instructions use a byte pointer
that indicated the byte within the word, and this worked well.

> 
>> The big advantage of having a line of computers with a
>> single architecture would be to ease moving from one machine to another that was
>> faster and/or bigger.  It also helped IBM, assuming they could consolidate their
>> OS and system software development and support.
> 
> That too, although BOS, TOS, DOS, OS/PCP, OS/MFT, OS/MVT, CP/CMS, TSS,
> and PS44 suggest that consolidating the system software didn't work
> out so well.

PS44, TSS, and CP/CMS were special cases. PS/44 was a special case, since
the /44 used the same platter disk as the 1130 (2315?), and no other 360
supported it. Also it was designed to be a real-time OS, whereas real-time
features were grafted on to OS/360 later. TSS, again, used special
hardware. CP/CMS was a "skunk works" project that took over the timesharing
space.  All the rest other than OS were mistakes. IBM was unable to get
even PCP to fit on the smallest machines, so DOS, TOS, BOS were written as
"temporary" systems which became permanent. Technically, PCP, MFT, and MVT
were "options" of OS/360, and they did share most of the same code base. I
think BOS may have been a development system used to bootstrap OS, and the
others were just developed from it.


-- 
Pete