8086 (was Re: more talking to the press.)

From: Sean 'Captain Napalm' Conner <spc_at_conman.org>
Date: Fri Nov 14 14:46:55 2003

It was thus said that the Great Eric Smith once stated:
>
> > Now, still beeing a strict 16 Bit CPU, this little trick
> > allows a 16 Bit user process to access up to 65K of 65K
> > segments.
>
> Not on the 8086, it doesn't. If you want independent 64K segments,
> you get a maximum of 16 of them. It wasn't until the 286 that
> they finally introduced proper segmentation.

  You mean 16 non-overlapping segments.

> > In fact, memory management on classic Macs was similar,
>
> Not really. The Mac has a single flat address space. The software
> chooses to carve it up into blocks called segments, but that's
> similar to the x86 segments in name only.

  If I recall, the early Macs did the software equivilent of virtual memory.
When you allocated memory you got back a pointer to a pointer of memory, and
you always had to reference through this indirect pointer to access the
memory, since the Mac (when the OS portion ran) could (and would) move
memory around.

  -spc (Not fond of the Mac-pseudo virtual memory scheme ... )
Received on Fri Nov 14 2003 - 14:46:55 GMT