x86-64 on i386 (was Re: Promoting i386 version over x86_64?)

Przemek Klosowski przemek.klosowski at nist.gov
Mon Dec 14 16:42:52 UTC 2009

On 12/14/2009 01:56 AM, Jon Masters wrote:
> On Sun, 2009-12-13 at 16:19 -0600, Chris Adams wrote:
>> Once upon a time, Jon Masters<jonathan at jonmasters.org>  said:
>>> Indeed. Paul, take a look at the Intel 64 ISA and you'll see it's a very
>>> different beast. Intel fixed a lot of the issues with the (more than 20
>>> year old really x86 ISA)
>> That would be AMD that fixed it, not Intel.  Intel tried to push
>> everybody to a new architecture (Itanium), while AMD revised and
>> extended i386 to 64 bits.  After Itanium failed to catch on in the
>> marketplace, Intel had to copy AMD's work.
> That's presumptuous and unfair. Sure, without AMD and others we'd likely
> be on Itanium (which I actually quite like as an architecture) but Intel
> 64 isn't just some copy-and-paste effort either.

I thought Intel adopted AMD 64-bit extensions pretty much wholesale. No 
shame in that---they were well-designed and well engineered. We the CPU 
consumers should be thankful for how well this was executed by both 
Intel and AMD. Kudos to Intel for acting in the best interest of their 
customers especially since they had so much invested in Itanium, both 
financially and in term of company pride.

While Itanium (aka Itanic :) was well-intentioned and looked good on 
paper, Intel/HP run into practical problems with the extent to which 
VLIW can be exploited by compilers, and with the hardware 
implementations, so that the actual performance is underwhelming. The 
Itanium siren song contributed to demise of SGI and wobbliness of HP so 
let's not be too nostalgic about it.

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