Yeah... I know my use of Google will hurt most of you... try to not too much
overreact please.
Me to Google:
In fact, the real question for me is is it worth to continue my project to run
HAC ADA compiler for FreeDOS. My current version take sometime 30 mins to run
Hello World on QEMU KVM, while taking 5 seconds in VirtualBOX. I like the
small, virtual machine code I think I could understand on HAC. Thinking to had
Allegro lib access.
In 2026, continuing your project to run the
HAC (Hacker's Ada Compiler) on FreeDOS is a niche but technically sound
endeavor, particularly if you value understanding the underlying virtual
machine architecture.
Addressing Performance (QEMU vs. VirtualBox)
The performance gap you are seeing (30 minutes vs. 5 seconds) is likely due to
how the hypervisors handle 16-bit real-mode code.
VirtualBox is optimized for end-user desktop virtualization and legacy guest
operating systems like DOS. Its "VT-x" or "AMD-V" implementations often handle
the transition between protected and real mode more efficiently for DOS guests.
QEMU with KVM is primarily designed for modern 64-bit server workloads. KVM
often struggles with VM exits caused by 16-bit instructions or frequent
hardware interrupts common in DOS, which can lead to the extreme slowdowns you
experienced.
Solution: If you must use QEMU, ensure you are using -machine type=isapc and
check if -accel tcg (pure emulation) actually performs better than KVM for this
specific real-mode task, as KVM isn't always optimized for 16-bit instruction
sets.
Is HAC Worth It?
Educational Value: HAC is a "Hello-world Ada Compiler" designed to be
small, quick, and fully programmed in Ada itself. Because it compiles to a
custom bytecode executed by a small virtual machine, it is an excellent "Swiss
knife" for learning how compilers and VMs interact.
Simplicity: Unlike the heavy GNAT compiler, HAC's "compilation leaves zero
files" (it can do everything in memory) and targets a subset of Ada, making it
manageable for a single developer to port or extend on FreeDOS.
Allegro Library Integration
The Compatibility Gap: Modern Allegro 5 does not support DOS. You would
need to target Allegro 4.2, which was the last version with native DOS support.
The Binding Challenge: Since HAC compiles to its own VM bytecode rather
than native machine code, you cannot simply "link" the Allegro C library. You
would need to:
Write "primitive" hooks in the HAC VM (the part written in C or Pascal
that runs on FreeDOS).
Expose these hooks to the HAC Ada environment so your Ada code can call
Draw_Sprite or Install_Keyboard.
Feasibility: This is very feasible because the HAC VM is designed to be
"hacker-friendly" and extensible.
Verdict: If your goal is a lightweight, transparent system where you can see
every moving part, continue the project. Use VirtualBox for development to save
time, and focus on extending the HAC VM to support Allegro primitives for
graphics.
_______________________________________________
Freedos-devel mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/freedos-devel
