DOS ain't dead

OS/2 extender (Developers)

posted by Ringding, 01.10.2025, 18:54

> https://www.os2world.com/forum/index.php/topic,3980.0.html

I tried to register an account at the OS2 world forum specifically to reply to the thread there, but that would require admin approval, which is not forthcoming.

From a reply in this thread:

> You can have 16/32 code or 32/64 code but not 16/32/64.

That’s what I thought, but it is incorrect. Long mode can deal with all three code segment sizes at the same time, as indicated by the very first table in the system programming volume of AMD’s architecture manual (“Operating Modes”). What you cannot have is VM86 mode. I verified PM16 on my current Linux installations last week (from a 32-bit task). One significant piece of functionality is missing, although this is just a limitation of Linux, not the machine architecture: having your own SIGSEGV handler intercept general protection faults from that 16-bit code segment. Unfortunately, the kernel does not understand this kind of code and will kill the faulting process directly instead of invoking its signal handler.

Complete thread:

• OS/2 extender - kerravon, 10.09.2025, 21:05 (Developers)
  • OS/2 extender - Rugxulo, 10.09.2025, 21:30
  • OS/2 extender - Ringding, 11.09.2025, 17:44
    • OS/2 extender - kerravon, 11.09.2025, 17:57
      • OS/2 extender - Ringding, 11.09.2025, 20:41
        • OS/2 extender - kerravon, 12.09.2025, 00:08
          • OS/2 extender - Rugxulo, 12.09.2025, 04:07
            • OS/2 extender - kerravon, 12.09.2025, 16:55
          • OS/2 extender - Ringding, 12.09.2025, 17:20
            • OS/2 extender - kerravon, 12.09.2025, 18:03
              • OS/2 extender - Ringding, 01.10.2025, 18:54
                • OS/2 extender - kerravon, 17.10.2025, 17:41