Honneywell multics? from panels. the inline phots in this message folks -smecc

[Stefan Skoglund (lokal användare)]

mån 2016-03-14 klockan 13:38 -0400 skrev Mouse: 
> > There is one axis along which I concede that things have advanced
> > since Multics, which is away from monolithic kernels -
> 
> Whether that is an advance or a regression depends on your priorities.
> I see good arguments each way.
> 
> > But the complete structing of the system around a segmented,
> > single-level memory system (at least, in terms of the environment the
> > user sees) is such a fantastic idea that I simply don't understand
> > why that hasn't become the standard.
> 
> Well, what was the largest virtual memory space available on various
> machines?  On the VAX, it was either one gig or two gig, depending on
> whether you count just P0 space or both P0 and P1.  When you're mapping
> objects of uncertain size, that seems awfully constraining - and,
> depending on the page table architecture in use, it can cost a lot of
> RAM to get even that much; the VAX, for example, needs eight megs of
> RAM to map one gig of space, and that doesn't even account for any
> memory used to back any of that space.  And, back in the heyday of the
> VAX, eight megs was a lot of RAM.

Which is one of the reason why the POWER architecture was done the way
it was done.
How much table space is needed is directly decided by the machine's
amount of RAM (in POWER 1 at least.)