80386 and x87 emulators on 80186 possible? \ VOGONS

80386 and x87 emulators on 80186 possible?

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First post, by Jo22

Posted on 2022-11-12, 08:48

Jo22 Offline

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Hi everyone,

There's something that just comes to my mind - does the 80186 have the same exception handling ability as the 80286 still?
So that TSRs like EMU87 or EMU386 can intercept, if needed?

I mean, the 80186 is often treaded as an 80286 minus Protected-Mode, minus Virtual Memory (no 80286 MMU), minus that 24-Bit physical address space.

But otherwise, it has the same enhanced Real-Mode capabilities over the 808x, right?
It has a real address decoder, it doesn't need to bother the ALU for that (the 808x way of doing it).

Thanks in advance.

Best regards,
Jo22

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Reply 1 of 3, by mkarcher

Posted on 2022-11-12, 15:30

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The 80186/80188 has support for interrupt 6 ("invalid opcode"), but most likely not for interrupt 7 ("coprocessor not available"). On the 80286, generation of interrupt 7 is tied to bits in the MSW (the machine status word, which evolved to CR0 on the 386). The 80186 does not yet have a MSW. As I understand it, the 80186 has no indication whether a numeric extension is installed or not.

Reply 2 of 3, by Jo22

Posted on 2022-11-18, 07:13

Jo22 Offline

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Thank you very much ! That explains a lot to me !

So there's at least a tiny chance getting EMU386
to run on something ancient as, say, a BBC Master 512.

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

Reply 3 of 3, by mkarcher

Posted on 2022-11-18, 11:35

mkarcher Offline

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Jo22 wrote on 2022-11-18, 07:13:

Thank you very much ! That explains a lot to me !

So there's at least a tiny chance getting EMU386
to run on something ancient as, say, a BBC Master 512.

I was wrong now. I wrote the previous message when I was on my mobile, but I rechecked the datasheet now. I said the 80186 "likely" doesn't support interrupt 7. In fact, it does. The Interrupt 7 enable bit is the top bit of the "relocation register", which is an 80186 specific feature.

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