Comment by StillBored

<i>So with the 80386, Intel finally abandoned their failed approach of segmented address spaces and joined the linear rest of the world. (Of course the 386 is technically still segmented, but let's ignore that).</i>

That seems an odd interpretation of how they extended the 286 protected mode on the 386. The 286 converted the fixed address+64k sized segment registers to 'selectors' in the LDT/GDT which added permissions/etc to a segment descriptor structure which were transparently cached along with the 'base' of the segment in generally invisible portions of the register. The problem with this approach was the same as CHERI/etc that it requires a fat pointer comprising the segment+offset which to this day remains problematic with standard C where certain classes of programmers expect that sizeof (void*) == sizeof (int or long).

Along comes the 386 with adds a further size field (limit) to the segment descriptor which can be either bytes or pages.

And of course it added the ability to back linear addresses with paging, if enabled.

Its entirely possible to run the 386 in an object=segment only mode where each data structure exists in its own segment descriptor and the hardware enforces range checking, and heap compression/etc can happen automatically by simply copying the segment to another linear address and adjusting the base address. By today standards the number of outstanding segment descriptors is limiting, but remember 1985 when a megabyte of RAM was a pretty reasonable amount...

The idea that someone would create a couple descriptors with base=0:limit=4G and set all the segment register to them, in order to assure that int=void * is sorta a known possible misuse of the core architecture. Of course this basically requires paging as the processor then needs to deal with the fact that it likely doesn't actually have 4G of ram, and the permissions model then is enforced at a 4K granularity. Leaving open all the issues C has with buffer overflows, and code + data permissions mixing/etc. Its not a better model, just one easier to reason about initially, but then for actual robust software starts to fall apart for long running processes due to address space fragmentation and a lot of other related problems.

AKA, it wasn't necessarily the best choice, and we have been dealing with the repercussion of lazy OS/systems programmers for the 40 years since.

PS: intel got(gets) a lot of hate from people wanting to rewrite history, by ignoring the release date of many of these architectural advancements. Ex the entire segment register 'fiasco' is a far better solution than the banked memory systems available in most other 8/16 bit machines. The 68000 is fully a year later in time, and makes no real attempt at being backwards compatible with the 6800 unlike the 8086 which is clearly intended to be a replacement for the 8080.