Some words of encouragement

Brad Normand
2012-02-24T17:26:22Z

I've been watching this list for a while and I'm happy development is
continuing! The last time I tried playing around with ELKS, I
couldn't even get things to compile, and had I succeeded, I got the
feeling I wouldn't be too impressed.

In case anyone's interested, my wishlist:

Support for 100% BIOS I/O (eventually I'd like to run this on
non-standard hardware, Sanyo MBC-55x, so any in/out opcode and
interrupt hooking will fail to work as intended). Where necessary,
BIOS RAM can be probed and this shouldn't be a big problem.

Support for reserving some low memory area (again due to hardware constraints).

Some method to transfer data to/from FAT12.

And, a question... how feasible would it be to run anything with 256KB
RAM? I was tempted to reply to the EMS code message because to make a
useful ELKS machine out of these, I may have to design a memory
expansion board, and I've got lots of 4MB SIMMs laying around.
Otherwise without kernel bankswitching support (or through EMS calls)
I believe I can do 960KB.

I also have a strange memory management idea that may be
interesting... Since 8086 is a 64KB segment oriented machine and you
are already bumping up against the limitations of that, and there is
talk of changing compilers... how crazy would it be to design a new
segmentation ABI to allow relocation of segments and still allow
programs to use more than 64KB?

I'm thinking something along the lines of, instead of using mov DS,AX
type instructions, these are changed to an OS call, so that the kernel
knows what segments the userspace is using, and when it has to
relocate data, it can simply rewrite the stored CS,DS,ES,SS of the
userspace, and next time the userspace needs to switch segments, it
asks the OS to do the dirty work. Managing >64KB allocations is
possible too but basically the program needs to request a 64KB window
into the data at a time. This would probably be pretty directly
applicable to a bankswitching scheme as a poor man's MMU.

Sorry for the craziness but I've spent many hours pondering this stuff
in the past... if there's interest I'd be happy to put together a
specification of sorts.