Posted by: vertigo« on: April 25, 2021, 23:04:01 »
Quoteit will be less efficient, i.e. slower, due both to having to specifically avoid what may be an optimal method and having to take code designed for other instruction sets and translate it first before processing it
First, they do not need to translate instructions if they intend to develop software stack (compiler's backend) and extract maximum performance by executing native code.
I may be misunderstanding, but it seems you're actually confirming my point. At some point, it will require a translation, since code that is written for one instruction set needs to run on another. Granted, this may have a very small impact on performance, but it's still one extra step and therefore at least a bit slower, even if negligible. Unless code is written specifically for the new instruction set.
Third, ISA created from scratch doesn't mean it must be less efficient than existing one. For example, decoding variable length instructions without clear boundaries in x86 case is not easy and it is said to be one of the reasons why x86 decoders need substantial amount of power and current CPUs are limited in instruction fetch bandwidth. Being still able to execute 30-years code may sound attractive, but it is quite a high burden for instruction decoder.
Not saying it must be less efficient, just that it might be since they may have been forced to use less than ideal methods in order to avoid infringement. Then again, it's also possible that they may have developed even better methods, since they weren't beholden to maintaining compatibility. And as I and the article mentioned, they would have gained some efficiency from being able to abandon old, unnecessary instructions, which is what you're referring to in regard to this. So my point was that there are likely elements involved that reduce the efficiency, ones that increase it, and ones that could go either way, so we won't know the total net improvement or reduction in performance until there are production samples to test, but it just seemed like they have a lot of things working against them.