Advanced Micro Devices Inc (AMD)

[pgerassi]

Wbmw:

Name one 64 bit CPU that can run its 32 bit OS and still use its larger 64 bit register set without a recompile. Couldn't do it. Alpha, Power required recompiles because they were brand new ISAs. MIPS required recompile to use 64 addressing and 64 bit data typeswhich required rewriting OS & drivers for 64 bit operation. Ditto for SPARC. Your objections are worthless.

8080 to x86 needed a reassemble going from 8 to 16 bits, but to get the most required rewriting for the new 1MB address space and x87. X86 to x86-32 needed the same things going from 16 to 32 bit. Yet everyone I know liked the x86 to x86-32 (386) transistion to get back to flat addressing from the segmentation models that existed before. But it still needed a recompile to use 32 bit modes (and the OS & drivers to get the 4GB addressing space).

Yet the conversion to x86-64 was so easy that many 64 bit applications could be ported to Long mode quickly (optimization took longer). Most OSes that were successfully using 64 bits on other ISAs (CPUs) ported before there was working silicon (on the simulators). With hardware becoming available, most just dropped in and worked. That points to how well the transistion was done. Many of the changes were welcomed (making flat addressing required which rids segmentation stuff is a biggie).

So I think that they cut out the parts of the medusa that were no longer needed or wanted. Pointed to other things that will someday go away. And still allowed backwards compatability, if desired. A fact that Intel and others fail to grasp. Grandfathering and not having to spend to change software are king. This King keeps x86 in its various flavors at the top of the revenue and profit heap. Every time Intel tries to cleanly break away, they have gotten burned (iap432, i860, i960 and now IPF).

Pete