On Thu, 9 Jun 2005 02:03:28 EDT, [EMAIL PROTECTED] wrote: >> still be maintaining instruction- and register-level compatibility >> with the microprocessors they were developing then?
> Really??? I mean how common is that now? It must be a very small > percentage. I was speaking specifically about the Intel x86 family. A lot of the machine code from the MS-DOS 1.0 days that doesn't reqire I/O and doesn't do finicky math on stack addresses will still run just fine. Registers have gotten bigger and more instructions have been defined, but 0x55 still pushes the base pointer (BP) register (which is now 32 bits wide), and 0x8b 0xec still moves the contents of the stack pointer register to the base pointer register (which are each now 32 bits wide). IIRC, there's even a "Virtual x86" mode still in the P4s. There definitely was in the 386, 486, and Pentiums I and II. TTYL, DougF KG4LMZ
