70's computers

[Paul Koning]

> On Oct 24, 2018, at 12:38 PM, Chuck Guzis <cclist at sydex.com> wrote:
> 
> On 10/24/18 5:36 AM, Paul Koning wrote:
>> 
>> Very different.  PPUs are real computers, vaguely like a PDP-8 in
>> fact but quite fast. The PPUs have major roles in the OS throughout
>> the 6000 series, not just in early versions.  
> 
> You obviously haven't spent much time in SSD (Special Systems).  I
> recall working on a transaction-oriented multiple-CPU system (tied
> together with ECS) where the PPs were little more than I/O processors.
> *None* of the main operating system code was in the PPUs, save, perhaps
> for DSD.
> 
> The reason for this was quite simple--PPs are terrible when it comes to
> block ECS transfers and having the PPs switch their attention between
> tasks whose CM lifetime was measured in milliseconds was impossible.  

Actually, no, my 6000 time was at the University of Illinois PLATO project.  It runs on NOS, which has both CPU OS code and substantial quantities of PP resident OS stuff.

PLATO is intensely dependent on ECS, far more than typical CDC software.  And in fact, several of its PPs talk via ECS, not CM.  Disk I/O, terminal I/O, these go via ECS.

	paul