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Subject:	Re: Adding 64-bit file support to DJGPP
From:	Georg Potthast <dosusb AT googlemail DOT com>
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The 64bit hardware does no longer support V86 mode. This mode was intended to allow 32 bit operating systems to run 16 bit applications, i.e. DOS applications.

Now the hardware has to be able to support 32 bit operating systems in 64 bit mode, like Windows XP. For this VT-X has been implemented which allows to emmulate a 32 bit PC in 64 bit mode. This is used by VirtualPC and friends.

Writing a Hypervisor that uses VT-X is really a lot of development since you have to virtualise just about anything. I evaluated an alternative Hypervisor just to see how much is left to implement to make it usable.

DJ Delorie is right to suggest MinGW as an alternative. As long as you do not access the hardware directly it is really easy to port a DJGPP program to MinGW.

Otherwise I think that a robust alternative is to put your DJGPP application together with FreeDOS on a disk image and package that together with a command line version of Qemu for Windows which is about 13 MB compressed. When the user starts your package he/she will start Qemu with FreeDOS starting your application.

I only need a 2 MB FreeDOS distro to run my DJGPP applications. Many of the Qemu files in the 13 MB package you do not need. So the entire package will probably add up to compressed 15 MB which is less than most Windows applications.


Am Freitag, 24. Mai 2013 16:55:18 UTC+2 schrieb RayeR:
> Well, I see there's already GCC for UEFI targets. So much more interesting would be to write some V86 monitor that switch from PM to V86 and allow running existing DOS programs. It would trap INT calls and translate it to UEFI calls. But I belive it's hard task, maybe complicated like Japhet's Jemmex...

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