> - I would like to read the whole RAM (mainly only 32 bit - 2 GB, but 4
> GB or even more in 64 bit are also interesting) and write it into a raw
> image (also called sometimes flat or .img).

The BIOS int 15.87 lets you access the first 4 GB, if you
want to access more than that, you have to do fancy stuff,
typically forcing you to do the work in assembly language.

You cannot modify HIMEMX for that easily: 36 bit addressing
is not so exotic, but if you lock a handle, it must get an
address inside the first 4 GB because of API limitations...

The highest physical addr is also limited to 4 GB, while the
total amount of available XMS can be up to 4 TB. Each handle
can access at most 4 GB, still enough :-).

You can modify JEMM386, though, as EMM386 never tells you
the actual address of your data (in original EMS hardware,
it did not even have one, only the page frame window had).
Each handle can refer to up to 256 MB of RAM in EMS API.

However, a modified JEMM386 would no longer be compatible
with any old DOS extender because the VCPI interface only
works with at most 4 GB address range and 4 kB phys pages.

If you modify HIMEMX to allow using > 4 GB RAM, as long
as max 4 GB per handle are used, and take the risk that
locking a handle can be slow (need move to first 4 GB if
you are unlucky) you still break EMM386 compatibilities.

PS: Any chances that JEMM386 will support int 2f func 4a15,
"install I/O virtualization handler" (MS EMM386 extension)
which would allow creating *virtual hardware* for FreeDOS?
Only few MS DOS drivers use it. Might be easier than JLM?
By the way, can JLMs support virtual DMA and IRQ creation?

> - Also interesting for disk cloning, reading a whole drive and storing
> it as a raw image.


Of course, instead of reading through 50 freshmeat matches
or 15 Heise matches for "disk image" to find which ones work
in DOS (Tom's software and FreeDOS are among the results),
you can also use a Linux boot CD/DVD/USB and use your dd ;-)
I am almost sure Heise HAS a disk clone tool for DOS, though!

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