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First post, by kruwi

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I have recently - out of curiosity - installed MS-DOS 6.22 in dosbox using a clean svn build, a 120 MB hard disk image and the dos 6.22 floppy images.

It works great - although I have not yet encountered any real "compatibilty advantages" compared to using just dosbox's builtin "dos" and mounting directories.

One thing I have noticed is that as soon as the "boot -l c" command is executed, dosbox by default switches to "cycles=max". Why is that the case? Isn't Dos 6.22 a real-mode-operating-system unless you run protected mode apps/games? Now I know how to fix this using the config file, but I am still curious why dosbox would switch to max when booting into MS-DOS.

My system: Acer Spin 1 laptop, CPU Pentium N5000, 4 GB of RAM, OS: Windows 10 64 bit.

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Reply 2 of 11, by kruwi

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Ok. And because of that by default dosbox will switch to dynamic core/cycles=max unless I manually alter the config to be core=normal, cycles=3000, for example? Is it because of the 64 bit OS?

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Reply 3 of 11, by Dominus

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nothing to do with the host OS. it's because by default cycles are set to auto and probably , as jmarsh wrote, your image loads emm386 (because just testing a DOS 6.22 floppy image does not set the cycles to max)

Windows 3.1x guide for DOSBox
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Reply 5 of 11, by kruwi

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Dominus wrote on 2020-01-07, 16:42:

nothing to do with the host OS. it's because by default cycles are set to auto and probably , as jmarsh wrote, your image loads emm386 (because just testing a DOS 6.22 floppy image does not set the cycles to max)

Yes, I have installed Dos 6.22 to a hard disk image. And yes, emm386 is loaded.

Interesting.

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Reply 6 of 11, by Dominus

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I see that I wasn't clear, "just tested a Dos 6.22 floppy image" was what I meant 😉

Windows 3.1x guide for DOSBox
60 seconds guide to DOSBox
DOSBox SVN snapshot for macOS (10.4-11.x ppc/intel 32/64bit) notarized for gatekeeper

Reply 7 of 11, by kruwi

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Wikipedia says:

"In the 80386 microprocessor and later, virtual 8086 mode (also called virtual real mode, V86-mode or VM86) allows the execution of real mode applications that are incapable of running directly in protected mode while the processor is running a protected mode operating system. It is a hardware virtualization technique that allowed multiple 8086 processors to be emulated by the 386 chip; it emerged from the painful experiences with the 80286 protected mode, which by itself was not suitable to run concurrent real mode applications well.[1]"

Very interesting indeed. I didn't know that before.

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Reply 9 of 11, by Dominus

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It happens, just not with the built in EMS.

Windows 3.1x guide for DOSBox
60 seconds guide to DOSBox
DOSBox SVN snapshot for macOS (10.4-11.x ppc/intel 32/64bit) notarized for gatekeeper

Reply 10 of 11, by kruwi

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This time it was me who wasn't clear 😉. I know it happens for protected mode games and for Windows 3.x. But why doesn't it happen with dosbox builtin memory managers?

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Reply 11 of 11, by jmarsh

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It does happen if you manage to load EMM386 in DOSBox's DOS.

V86 mode doesn't really achieve much (except create a lot more work for the emulator) so there's no reason to have it active by default. It does get activated by a few games (Wing Commander series).