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OS/2 - ArcaOS 64Bits Kernel Discussion
Doug Bissett:
--- Quote from: Andreas Schnellbacher on December 11, 2020, 10:42:43 pm ---How I understand it, its mainly a question of adding PAE to OS/2. 64 bit wouldn't be the next step, and will never be. With PAE there would exist 4 GB address space per application. 32 bit variants of many OS have that implemented.
--- End quote ---
PAE already exists for OS/2. QSINIT uses it with the RAMDISK, and there is a program interface to use it in other ways (pretty limited, I think). The problem is, that the RAMDISK is the only application that uses it, Nobody else has stepped up to expand on it.
I agree that OS/2 will never be 64 bit. Somebody may think they can do it, but it would be a lifetime project. I doubt if it would be possible to even identify all of the things that would need to be done to make the change.
Lars:
I don't know how PAE actually works.
But what I know is that the support that QSINIT / the AOS loader offer to access memory > 4 GB physical address is effectively based on offering 512-byte sectors to use by a requester.
This is not surprising (and also pretty clever :-)), as the QSINIT supplied RAM disk driver uses that memory as file data sectors (in the real sense of the word).
However, that also means that they offer their own sector addressing API for use by other applications but there can only be ONE user at any one time which means you will then have to give up on the RAM disk support and you cannot have multiple applications using different parts of that memory at the same time.
In short, this extension is not generic byte addressable support of memory as the CPU understands it. It's not memory management as we know it and therefore applications have to be written to use it.
Rather think of it as if you were accessing external video memory on an adapter card. A special purpose for a special user.
Andreas Schnellbacher:
--- Quote from: Doug Bissett on December 12, 2020, 09:25:48 am ---PAE already exists for OS/2.
--- End quote ---
That is wrong. The question is how to make it available for the system, not for a RAM disk. Other OS do this.
What would you gain with a RAM disk, if the usual memory exhausts? Don't mix up memory space with hard disk (or RAM disk) space.
BTW: I can't comment on Lars' post.
Doug Bissett:
--- Quote ---That is wrong. The question is how to make it available for the system, not for a RAM disk. Other OS do this.
--- End quote ---
It is not wrong. PAE exists. The problem is, that there is no real API to use it. Some programs could use it, as it is (raw memory space), for some things, but that could be expanded, if somebody knows how to do it. The one program, that comes to mind, is CLAMD.EXE, which loads huge amounts of data into upper shared memory space (at least it is UPPER shared space). That could live in PAE memory, with a bit of work. I am sure there are other things that could use it, without having to write a whole API. Another possibility is to use PAE memory for disk cache. At least the source code for JFS, and FAT32, is available.
Perhaps some current API could be redirected to use PAE memory, rather than upper shared memory (for instance). There are possibilities, if someone knows how to do it, and is willing to try. Part of the problem is, that not all computers have more than 4 GB of physical memory, but most new computers do have more, and it could be used. Another part of the problem is that many OS/2 programmers have lost the ability to do much more than port programs from other platforms (which is actually what is causing the problem, in the first place, but is probably necessary), and they just don't know how to do things like this any more. Those who do have the knowledge are far to busy doing more important things.
Any part of the current memory space, that can be eliminated, leaves more space for other things to use. The RAMDISK works very well, but there is a limit to how much space you can actually use as a disk drive that needs to be loaded at boot time, and unloaded at shut down, if you want to use it with data that must to be saved over a boot (in some cases, the RAMDISK can still contain the contents, but there is no guarantee about that).
Don't say "you can't do that". Ask yourself "how can i do that". That sort of thinking produced the QSINIT package, and the QSINIT package has enabled more than just the RAMDISK. It also enables using fragmented memory, that is often found in new computers. It is essential to the UEFI support that is being developed (which includes better support for DOS/WinOS2), and it will probably be used for many more things as the need arises. Small steps lead to greater things.
Andreas Schnellbacher:
Doug, just try to understand what Lars wrote.
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