Re: Taroon-list Digest, Vol 4, Issue 51

[Brian Long <brilong cisco com>]

Jeff,

Read carefully the release notes of RHEL 3 x86_64 and it tells you the
differences (why there is a ia32e and x86_64 kernel).  Remember, neither
chip is "truly" 64-bit in all manners.  For example, the AMD Opteron can
"only" address 48-bit memory. I think that's still plenty for most of
us.

FYI, the EM64T and Opteron are very similar except for the memory
controller.  Each Opteron has a on-chip memory controller to control its
own bank of RAM.  The EM64T, just like other Xeons, uses the slow Front
Side Bus which is still running at 533MHZ.  If you have a memory
intensive app, you'll easily saturate the FSB on a dual-Xeon machine,
whereas the Opteron will perform much better (assuming a dual Opteron
machine where each Opteron has it's own bank of RAM).

/Brian/

> sheesh...  But I am trying to figure out the benefit of the EM64T
> chips... maybe someone could explain that to me...  The AMD64 chips are
> true 64 bit chips, with the ability to run 32 bit code natively... but
> the EM64T chips, if I read the Intel info correctly, are simply IA32
> chips with 32 extra registers and code to run 64 bit software/OSs.... 
> SO...  given that, wouldnt the EM64T chips still lag behind the AMD64
> chips, given the differences there??

-- 
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