Emulator opcode FE /7 iw magic opcode? \ VOGONS

Emulator opcode FE /7 iw magic opcode?

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First post, by superfury

Posted on 2015-09-01, 09:33

superfury Offline

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I'm using the FE /7 iw(immediate word) opcode in my emulator to execute handlers hardcoded in my emulator (function 0 being the BIOS POST, all other handlers are dynamically allocated). I know Dosbox uses it in the same way too to handle it's BIOS and MS-DOS interrupt handlers.

Are there other emulators using this opcode in this way as well or are only Dosbox and my x86EMU using the opcode this way? Does VirtualPC, VirtualBox, QEMU etc. use it too?

Author of the UniPCemu emulator.
UniPCemu Git repository
UniPCemu for Android, Windows, PSP, Vita and Switch on itch.io

Reply 1 of 3, by peterferrie

Posted on 2015-09-01, 17:14

peterferrie Offline

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I don't know of any other emulator that uses that instruction.
VirtualPC, for example, uses an illegal CMPXCHG-based sequence as one method. VMware uses an I/O port as one method.
I have forgotten how QEMU does it, and I haven't looked at all at VirtualBox.

Reply 2 of 3, by superfury

Posted on 2015-09-02, 06:53

superfury Offline

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And Bochs? How does Bochs use it (if at all)? Or does it use an actual BIOS instead of doing it in the emulator?

Author of the UniPCemu emulator.
UniPCemu Git repository
UniPCemu for Android, Windows, PSP, Vita and Switch on itch.io

Reply 3 of 3, by peterferrie

Posted on 2015-09-02, 16:18

peterferrie Offline

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Bochs has a magic port, too.

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