3 ms·

I don't think the parent said that it's interpreted, only that it sits on a translation layer which is true.

skissane 5y ago
Oh yes. But the parent made it sound like having a "translation layer" makes it somehow unique. Contemporary IBM i, the "translation layer" is a modified form of compiler intermediate language copied from IBM's AIX/etc compilers, and as such isn't really fundamentally different from what happens on other platforms. It also made it sound like the translation layer had a performance cost – in itself, it doesn't, any more than LLVM IR has a performance cost. Some of the entities the bytecode/IR allows you to manipulate – such as 128-bit pointers – likely have some cost, but that is a cost of those entities, not of having a bytecode/IR in itself. Not saying there is nothing unique about AS/400. The single-level store is a big one, although in more recent decades there has been a big move away from it (teraspaces, PASE, migration from Classic to J9 JVM). I think the history of 38/400/i could be described like this: it started out with some very innovative, even in some way alien ideas – capability addressing, single address space single-level store, having a bytecode (as opposed to the real hardware's assembly language be the public interface to the OS), primitive object-orientation backed into the OS, a relational database embedded in the operating system (although how deeply integrated it really is has never been that clear), etc. At the same time, it mixed that up with some far less innovative traditional IBM technologies – COBOL, RPG, EBCDIC, block mode terminals, SNA, etc – so even from the start it was some odd hybrid of cutting-edge and trailing-edge ideas. But, gradually since, it has been moving away from that odd mix towards become a much more mainstream system. While the old MI bytecode was a public interface, the new MI bytecode documentation is only available under NDA, and is basically the same as IBM's proprietary compiler intermediate representation on their other platforms. The single address space single-level store exists, but now programmers are encouraged to run their code in a more traditional separate address architecture (teraspace) instead. With the move to POWER, an AIX compatibility subsystem (PASE) was introduced, and more and more code was ported from AIX – and more recently open source packages from Linux. Java was ported to it, and programmers were encouraged to develop in Java – and while IBM's original AS/400 JVM, the "Classic JVM", integrated Java with the original AS/400 single address space world, at some point it was replaced by a port of IBM J9 from AIX running in a teraspace, and now it really behaves no differently than J9 on any other platform does. It is a system which started out as a weird hybrid of the innovative and the traditional, but which has been gradually evolving to be come more and more mainstream, without dropping the backward compatibility necessary to support that original weird hybrid.

Oh yes. But the parent made it sound like having a "translation layer" makes it somehow unique. Contemporary IBM i, the "translation layer" is a modified form of compiler intermediate language copied from IBM's AIX/etc compilers, and as such isn't really fundamentally different from what happens on other platforms. It also made it sound like the translation layer had a performance cost – in itself, it doesn't, any more than LLVM IR has a performance cost. Some of the entities the bytecode/IR allows you to manipulate – such as 128-bit pointers – likely have some cost, but that is a cost of those entities, not of having a bytecode/IR in itself. Not saying there is nothing unique about AS/400. The single-level store is a big one, although in more recent decades there has been a big move away from it (teraspaces, PASE, migration from Classic to J9 JVM). I think the history of 38/400/i could be described like this: it started out with some very innovative, even in some way alien ideas – capability addressing, single address space single-level store, having a bytecode (as opposed to the real hardware's assembly language be the public interface to the OS), primitive object-orientation backed into the OS, a relational database embedded in the operating system (although how deeply integrated it really is has never been that clear), etc. At the same time, it mixed that up with some far less innovative traditional IBM technologies – COBOL, RPG, EBCDIC, block mode terminals, SNA, etc – so even from the start it was some odd hybrid of cutting-edge and trailing-edge ideas. But, gradually since, it has been moving away from that odd mix towards become a much more mainstream system. While the old MI bytecode was a public interface, the new MI bytecode documentation is only available under NDA, and is basically the same as IBM's proprietary compiler intermediate representation on their other platforms. The single address space single-level store exists, but now programmers are encouraged to run their code in a more traditional separate address architecture (teraspace) instead. With the move to POWER, an AIX compatibility subsystem (PASE) was introduced, and more and more code was ported from AIX – and more recently open source packages from Linux. Java was ported to it, and programmers were encouraged to develop in Java – and while IBM's original AS/400 JVM, the "Classic JVM", integrated Java with the original AS/400 single address space world, at some point it was replaced by a port of IBM J9 from AIX running in a teraspace, and now it really behaves no differently than J9 on any other platform does. It is a system which started out as a weird hybrid of the innovative and the traditional, but which has been gradually evolving to be come more and more mainstream, without dropping the backward compatibility necessary to support that original weird hybrid.