[Info-vax] Chinese Alpha?

[Bob Koehler]

In article <4fa2eef6$0$288$14726298 at news.sunsite.dk>, =?ISO-8859-1?Q?Arne_Vajh=F8j?= <arne at vajhoej.dk> writes:
> 
> I would think that x86-64 is similar to x86 in somewhat
> the same way as VAX was similar to PDP-11.

   I was under the impression that adding 64 bit to x86 was something
   like adding 23 bit to PDP-10, or 32 bit to 8086.  Existing code
   continues to run.

   VAX to PDP-11 was different.  The VAX instruction set is not the
   PDP-11 instruction set, although early VAXen had two instruction
   sets:  VAX and compatability mode (a subset of PDP-11).  CHMU was 
   used to switch to the compatability mode instruction set when 
   running PDP-11 user mode code.