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OS/2 - ArcaOS 64Bits Kernel Discussion

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Ok,that refers to the logical/linear address (the one the CPU translates to the physical address via the paging mechanism). That could remain 32-bit.
Still, your memory management has to support 64-bit physical addresses. The memory is a global resource, a physical address is unique, in contrast to a logical one.
And this means a rewrite of the memory management.

Martin Iturbide:

I slip the topic, since it is a very interesting discussion.


Martin Iturbide:

Since the OS/2 kernel is not open source, I always thought that some alternative for OS/2 kernel evolution issue will be to replace completely the OS/2 kernel for a different 64bit kernel and interpret the OS/2 personality with the IBM binaries over it. People will complain that the kernel is the OS, but I'm starting to believe that OS/2 is more about the experience of the desktop and being able to run the OS/2 applications software that we like and use.

Maybe like Project 2ine tried to do, but not re-implementing all the OS/2 API (like PM) in one shot, but trying to use first the IBM Binaries tricking them to think they are running on the OS/2 kernel while not. 2ine tried to do a Wine for OS/2 under Linux, maybe we should bring the OS/2 components over a different kernel instead. Of course, all OS/2 drivers and application that uses a driver (like some utilities) will turn useless.

I just trying to think how something like that should look from a architectural high level point view.


Roderick Klein:

--- Quote from: Lars on December 10, 2020, 11:22:46 pm ---Physical addresses under OS/2 are also limited to 32-bit. Which means your approach of "4 GB of physical memory per core" cannot work.
You cannot address beyond the physical 4 GB boundary with the current OS/2. You would have to completely reimplement OS/2 memory management to support 64-bit physical addresses (and linear addresses).
Which becomes a massive problem because many new systems "waste" physical address space below the 4GB boundary by simply leaving it unused or by placing large regions of "non system-memory", for example, PCI address space.
And that's why there are machines that have 4 GB of system memory but can only use 2.5 GB or so under OS/2. That's because the other 1.5 GB of system memory are physically addressable beyond the 4 GB physical address boundary.

--- End quote ---

It might be possible to use the ArcaOS loader to use memory in large programs above the 4 GB memory border. But these are rough idea's. It would make more sense to see if you can modify large GCC applications to use such scheme. Do not modify the kernel, modify the application. Hopefully next year we can look further at this and see if simple proof of concept can be delivered.  To be clear again this is an idea.

Roderick Klein

Andreas Schnellbacher:
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.


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