On Sunday 30 October 2005 4:57 pm, Ben Scott wrote: > From what I've read, I'm not sure how accurate that is. AMD64 (and > Intel's clone of it, EM64T) enable CPU modes which support a native > address space larger then 32 bits. Not the "32 bit window into a > larger space" that Intel PAE provided, but true native addressing. > You also get 64 bit registers and ops, but you had those already with > various ISA extensions. > > I say "larger address space" because I don't actually know how large > the possible address space of AMD64 is. Current implementations may > not support a full 64 bits of address space. But as I recall from my > machine architecture course at UNH, the Alpha chips of the day didn't > really implement a full 64 bits of address space all the time, either. > It's inefficient to process 64 bits of address math when you only > need 40 bits or so. Or so I recall. My memory is really dusty here. The AMD64 chip supports full 64-bit virtual address space. However, only 52-bits are currently used for physical addressing. In 64-bit mode the address space is flat. (A separate address space for code, stack and data segments is also possible). A 32-bit app running in a 64-bit OS runs in compatibility mode where the legacy 32-bit and 16-bit segmentation addresses are mapped to the lower 32-bits of virtual address. A 32-bit OS operates in a legacy mode.
According to industry sources, neither Intel nor AMD will be producing 32-bit chips after next year. I personally see AMD cutting into Intel's market share on personal systems and low end servers since it is a better performing chip than Intel's EM64T line. The high-end server market will see IBM, HP and Sun duke it out. -- Jerry Feldman <[EMAIL PROTECTED]> Boston Linux and Unix user group http://www.blu.org PGP key id:C5061EA9 PGP Key fingerprint:053C 73EC 3AC1 5C44 3E14 9245 FB00 3ED5 C506 1EA9 _______________________________________________ gnhlug-discuss mailing list gnhlug-discuss@mail.gnhlug.org http://mail.gnhlug.org/mailman/listinfo/gnhlug-discuss
