[Info-vax] OT: IA-128 ???

[Arne Vajhøj]

glen herrmannsfeldt wrote:
> Arne Vajh?j <arne at vajhoej.dk> wrote:
> (snip)
>  
> < The general accepted definition of a X bit computer is the size
> < of addresses not the size of registers.
> 
> I suppose so, but mostly on machines where the register size
> equals the address size.  Also, do you mean virtual address
> size or physical address size?

virtual

> < There are good practical reasons why they often are identical,
> < but they do not have to be.
> 
> And for those machines where they aren't the question is open.
> Consider processors like the 680x0 or some CRAY machines with A 
> registers (for addressing) and D registers (for data) that might 
> have different sizes.

This is exactly the most typical case where the bit'ness of a computer
and the register size differs.

> < Even a VAX has somewhat 64 bit general register because q operations
> < could use Rn and Rn+1.
> 
> That pretty much doesn't count unless at least add, subtract,
> multiply, and divide can be done on the full size.  

VAX did not support much (only mov, clr and the odd E's), but
even if they had had full support - it would still have been
a 32 bit processor.

> The 8086 has a 20 bit address space but was not considered
> a 20 bit processor.

It was not a 20 bit flat address space.

>                     IA32 processors starting with the PentiumPro
> have a 36 bit physical address bus, but aren't 36 bit processors.

Physical does not count.

It is common with unusual physical address sizes.

Arne