Integer conversions too pedantic in 64-bit

[Walter Bright]

Kagamin wrote:
> Walter Bright Wrote:
> 
>> Actually, you can have a segmented model on a 32 bit machine rather than a
>> flat model, with separate segments for code, data, and stack. The Digital
>> Mars DOS Extender actually does this. The advantage of it is you cannot
>> execute data on the stack.
> 
> AFAIK you inevitably have segments in flat model, x86 just doesn't work in
> other way.  On windows stack segment seems to be the same as data segment,
> code segment is different. Are they needed for access check? I thought access
> modes are checked in page tables.

Operating systems choose to set the segment registers to all the same value 
which results in the 'flat' model, but many other models are possible with the 
x86 hardware.