At 11:07 PM 3/27/2004 +0100, tom ehlert wrote:
>>> someone said EMM386 is incompatible with HLT instruction?
>
>MD> EMM386 uses the HLT instruction for its own purposes, but it
>MD> does a check if the HLT is coming from itself or externally.
>MD> Other than that, it looks like HLT causes the expected HLT
>MD> behavior when the exception handler is triggered (since HLT is V86
>MD> illegal). Tom Ehlert would probably know the most about this if
>MD> you need more info, since I believe it's his coding for the HLT
>MD> mechanism in EMM386.
>
>
>AFAIR, the emulated behaviour is similar to
>
> if (opcode == HLT)
> if (source is in EMM386 V86 device)
> {
> do something clever as commanded by V86 part
> }
> else
> {
> NOP
> }
>
>I may be wrong, but it probably never does HLT.
No, it looks like EMM386 does a real live HLT, but what the ramifications of that in
the protected mode handler are, if any, I don't know. Never coded a HLT in my life.
Of course, I never coded a WBINVD before either and now look at things.
Once EMM386 gets debugged VCPI, I'm probably not going to be diddling around the
EMM386 code much and generally causing trouble, other than wanting at some point to
add the shared EMS/XMS memory pool feature which it should really have (although not
necessary for a FreeDOS 1.0 release). VCPI support was final personal goal starting
from the first HIMEM >64M coding support, by getting more people to use it along with
EMM386.
Since you're the maintainer and overall "big picture" operations man on EMM386, and
I've just been handling the addition of a couple of features to get things working the
way I wanted, I don't have much of an opinion to offer on the RAM ROM INT15 <whatever>
options. My only observation is the typical one that reasonable Microsoft
compatibility is probably a good thing unless it's minor or gets in the way of an
enhancement or user compatibility (I like your suggestion to use percentage of
extended memory for VCPI much better than using Microsoft's fixed 256K for example).
You may find that command line option stuff as dreary as I do, but I think you're best
person to ultimately judge what EMM386/HIMEM options are deemed best. I've got no big
complaints with what you had done with them before I butted in.
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