Re: Intel vs AMD x86-64

[Bill Davidsen <davidsen@tmr.com>]

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