Re: Whizzy New Feature: Paged segmented memory

[Anthony DeRobertis]

On Tuesday, January 8, 2002, at 12:11 PM, jtv wrote:

>
> And, of course, the same for all other software.  But for a 
> highly secure
> project, for instance, that might be worth it.

I'd imagine most things would just work. It's only going to be 
the things that make assumptions about memory layout that will 
break.

I picked X as an example because it cares quite a bit about 
memory layout, especially when mapping in framebuffers and 
whatnot.

>
> 68K has predecrement/postincrement addressing modes (I'm not sure that
> counts as "forcing" the stack to grow downwards);

The address stack on 68K grows downwards because JSR, BSR, etc. 
do the stack manipulation for you.

Sure, you _could_ use JMP and BRA and maintain your own linkage, 
but that'd take a large performance hit. Much larger than making 
the data stack grow upwards, I dare say.

>  PPC has a symmetrical
> load/store-with-update IIRC.

Right. I don't think it cares. Nice architecture ;-)