Author: Robert Hyatt
Date: 08:57:58 07/01/03
Go up one level in this thread
On June 30, 2003 at 21:03:30, Tom Kerrigan wrote: >On June 29, 2003 at 23:50:11, Robert Hyatt wrote: > >>On June 29, 2003 at 06:35:02, Tony Werten wrote: >> >>>On June 28, 2003 at 14:23:50, Robert Hyatt wrote: >>> >>>>On June 28, 2003 at 12:12:15, Jay Urbanski wrote: >>>> >>>>>On June 28, 2003 at 10:33:45, Robert Hyatt wrote: >>>>> >>>>>>Those are not true 64 bit processors. Supposedly 32 bit stuff runs just >>>>>>fine on them, but they have 64 bit extensions. >>>>> >>>>>How is Opteron not a true 64-bit processor? >>>> >>>> >>>>Because it executes 32 bit instructions _also_. >>> >>>P4 and AMD also execute 16-bit instructions, so they are 16 bit processors ? >> >>Not pure 16 bit no. Not pure 32 either. >> >>Check out "Cray" for a better example of a pure architecture. >> >>All math is 64 bits. All address arithmetic is 32 bits. Different >>instructions, functional units, and registers for each. No kludges about >>gating 32 bits with 32 high-end zeroes and that kind of stuff. >> >>But in the case of opteron, at least at first look, it appears to be a 32 >>bit machine with 64 bit instructions layered on top. > >Are you kidding me? > >The "bitiness" is the width of a chip's datapath, right? Yes. But there is more. A chip made to do 64 bit operations as its _normal_ mode of functioning is a 64 bit chip. A chip that does 32 bit operations normally, with 64 bit add-ons, is not really a _full_ 64 bit chip. That was, and is, my point. > >The Athlon and Pentium quite obviously have a 32 bit datapath so they are 32-bit >chips. The Opteron has a 64 bit datapath so it's a 64-bit chip. > >I don't know what you mean by "64 bit instructions layered on top." > >-Tom It runs X86 natively. That is a 32 bit instruction set.
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