🚀 go-pugleaf

John Levine <jo...@taugh.com> wrote:
> In article <1355830485.555945700.866...@news.eternal-september.org>,
> Peter Flass  <peter...@yahoo.com> wrote:
>>> 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.
> 
> That's right.  I know of a similar character addresssing kludge in the
> GE 635.  It was OK, but the profusion of byte instructions added to
> the later models of -10 suggest that it didn't work that well.
> 
> The 360 design was clever that the addresses in the architecture were
> big but base registers kept the instructions were small, so only the
> registers had to be 32 bits.
> 
>>> 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. 
> 
> More to the point, the /44 only implemented a subset of the 360's
> instruction set, so even with different peripherals it couldn't run
> any other OS.

I understand there was a later microcode update so it could run OS/360.

> 
>> 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.
> 
> Yes.  I never entirely understood the difference between BOS and DOS.
> I realize that BOS could run in 8K and DOS needed 16K, but what else
> did BOS leave out?
> 

I don't know that much about BOS either. I used to think it was a subset of
OS, but Bitsavers has some manuals and it appears it was a subset of DOS.
I'll have to read the manuals. I would assume it at least left out
multiprogramming. I think BOS could be run from cards.


-- 
Pete