[RC5] AMD X86-64 port

Richard Menedetter ricsi at gmx.at
Mon Apr 28 23:45:16 EDT 2003


Hi gentryj!

28 Apr 2003, gentryj at gci.net wrote:

 g> However, AMD's 64 bit chip doesn't appear to be native 64....
what do you mean by "native 64" ?
Hammer is an improved athlon, whos ALU can also handle 64 bit values in the 64
bit mode. (PC and pointers are also 64 bit)
(but hammer still defaults to 32 bit values, you have to enable 64 bit values
by the use of special prefixes in the code.)

There is also a legacy mode where the hammer can run standard 32 bit OSes
natively. ("faster athlon" with sse2)

And in 64 bit mode, there is a compatibility mode, where you can run old 32 bit
apps inside of the 64 bit OS.

 g> (I'm still slightly confused about how they are claiming a 64 bit CPU
 g> can actually perform better at 32 bit applications?!?).
Because the 64 bit cpu is also a native 32 bit CPU, with some improvements.
These improvements (integrated mem. controller -> shorter latencies, larger
cache, larger TLBs, larger reservation stations, better branch prediction, MUCH
better SMP scalability) makes hammers run code faster than equally clocked
athlons.

The 64 bit part is only an extension to the existing IA32.

 g> IMHO, it could really go either way.
 g> Depends on if AMD is telling the truth.
hmmm ... what do you mean ?
first benchmarks are out ... you can see for yourself.
(PS: AMD has only released the server CPUs ... which are clocked lower ...
consumer CPUs should come at higher clockrates in september if AMD manages to
get heigh yields at higher clocks.)

 g> James / Warbird

CU, Ricsi

-- 
|~)o _ _o  Richard Menedetter <ricsi at gmx.at> {ICQ: 7659421} (PGP)
|~\|(__\|  -=> As long as I can remember, I've had amnesia <=-
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