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I read on wikipedia that the x86_64 ISA. Which is the 64 bit version of the x86 set. Is Backwards compatible with software written for the x86 architecture not because of emulations but because it is hard-wired into the chip.
Because the full x86 16-bit and 32-bit instruction sets remain implemented in hardware without any intervening emulation, existing x86 executables run with no compatibility or performance penalties, whereas existing applications that are recoded to take advantage of new features of the processor design may achieve performance improvements.
I really don't know much about cpu design. But some of the transistors inside there are used for just that backwards compatibility or not? Would a a cpu that supports a pure 64bit ISA have more space left because the parts that are for the backwards compatibility are gone? Is there such a cpu? Is there an 64bit ISA somewhere? Maybe planned?
Junaga
Posted 2016-09-08T16:42:07.510
Reputation: 66
You do understand that x86_64 (AMD64), is a x86 extension, that AMD developed. Yes; There is hardware that decodes what the extension is, but in the exact same way, as any x86 instruction is decoded. There are many people that think, x86 architecture is to complicated, because of its ability to decode 8-bit and 16-bit instructions. Intel does not agree, consumers do not agree, otherwise Intel wouldn't continue to support those legacy instructions. – Ramhound – 2016-09-08T16:54:28.487
Yes, I did read that.^^ I really think that such a processor that needs to support only a 64bit related ISA is better. And I think that Intel heads share that opinion, else wouldn't have done such an afford in creating the IA-64 ISA for the Itanium series.
sorry. was out of space here is the source of the quote https://en.wikipedia.org/wiki/IA-64#Itanium_9500_.28Poulson.29:_2012
– Junaga – 2016-09-08T17:05:46.343If it was better then the market would have accepted it. Intel clearly does not agree anymore, since they have not devloped any new IA-64 products, in years. Futhermore Intel made a huge mistake not making x86 support a possible option IA-64, to easte the tranisition period, between x64 and IA-64 – Ramhound – 2016-09-08T17:07:04.960
hmm. okeay you are right. the jump was to fast for the developers there was just still not enough x86 software alternatives out there. besides that: I want to know if there is any such processor out there with any such ISA. – Junaga – 2016-09-08T17:09:44.273
Itanium is it. ARM has 64-bit chips also but like x64, the ARM chips, support the 32-bit instructions also. – Ramhound – 2016-09-08T17:12:37.547
2ARMv8-A Architecture. At the end of the day. ISA architectures which do not support the previous architecture, are bound to fail. Cell architecture is one such example. It was different enough from existing architectures, that developing was more difficult, it wasn't even similar to previous IBM architectures let alone x86 or ARM. – Ramhound – 2016-09-08T17:15:15.960