🚀 go-pugleaf

Rich Alderson <ne...@alderson.users.panix.com> writes:

> Charles Richmond <nume...@aquaporin4.com> writes:
>
>> On 8/9/2018 1:45 PM, Rich Alderson wrote:
>>> Elliott Roper <nos...@yrl.co.uk> writes:
>
>>>> On 8 Aug 2018, hanc...@bbs.cpcn.com wrote
>>>> (in article<21aaeee8-c41a-4442...@googlegroups.com>):
>
>>>>> Bitsavers uploaded the system manual for the PDP 11/40.
>
>>>>> http://www.bitsavers.org/pdf/dec/pdp11/1140/DEC-11-H40SA-A-D_PDP-11_40_System_manual.pdf
>
>>>>> 358 pages, undated.
>
>>>> Thanks. Unbounded nostalgia. Was there ever a more elegant computer than a
>>>> PDP-11?
>
>>> Yes, many.
>
>> *Not* that I disagree...  but which other computers do you find elegant???
>
> My first computer was the IBM 1401.  *Not* an elegant architecture, but not
> without points of interest.

1401 was my first also.  One could do quite a bit in a small amount of
storage.  The A and B registers would tell you about the data the
previous instruction processed.  (Usually where the word mark was.)
Word marks were like the trailing null with C strings without the bother.

A shame none of that carried over to the S/360.
We could have had a 7 bit character with one bit reserved for the word mark.

> The first I fell in love with was the IBM System/360, thanks to a high school
> graduation gift from a sweetheart, Germain's _Programming the IBM 360_.  One of
> these days I'm going to put his simulator on Hercules and go through the
> exercises just for giggles.

Likewise, my next system was S/360 and I accumulated extensive
experience with the machine.  My first impression was that the machine
was over-complicated, on purpose.  The lack of sector addressing on
the disks is my best example.  After using disks for years on a 1440,
disks became more complicated than I thought they should be.
3270s are another example.  A simple thing like screen addressing
couldn't be done with row/column numbers in bytes?

The 24 bit addressing was more a failure in the programming department
than in hardware design.  Why any programmer would attempt to use
the high order byte for data instead of just assuming it would be
part of the address some day is a mystery.  IBM stepped in it big
putting a 3 byte address right in the DCB.  A DCB without a version
number or other reliable marker.  Still a problem to this day,

I've done huge amounts of assembly programming and the instructions
get the job done.  Issues with the base registers are easy to deal with
once you figure out that each subroutine should have it's own base
register, don't attempt to make all code addressible at once.

-- 
Dan Espen