Re: Intel vs AMD x86-64

Bill Davidsen
2004-02-27T03:16:00Z

Timothy Miller wrote:
>
>
> Nakajima, Jun wrote:
>
>> Yes, that's the very reason I said "useless for compilers." The way
>> IP/RIP is updated is different (and implementation specific) on those
>> processors if 66H is used with a near branch. For example, RIP may be
>> zero-extended to 64 bits (from IP), as you observed before.
>>
>
> This is obviously an extremely minor nit-pick, because we're talking
> about one instruction here with an interpretation that is far from
> obvious, but given that there are now only two architectures which
> support x86-64, did Intel choose to do it differently from AMD because
> it was poorly defined, or because it wasn't important enough to want to
> impact the efficiency of the design?

How about because they messed up trying to clone the instruction set?
Never attribute to malice what can be explained by stupidity. <-(quote)
>
> There are people who would go way out of their way to get a 5%
> improvement in performance or decrease in size. If using 66H with near
> branches could in some way do that, they would really really want to use
> it. This is why I'm curious.

--
bill davidsen <davidsen@tmr.com>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979