Re: Re: Comment on Memory Management FAQ

Sorry George, you completely mixed up everything.

> Conclusion:  FDXMS passively provides services directly for programs 
> that can switch themselves from real mode to protected mode, or 
> indirectly via VCPI or DPMI for programs that don't.  While FDXMS itself 
> does *not* provide VCPI or DPMI.  So if such services are required, they 
> must be provided by loading emm386, himem.sys, or the like.   Also, 
> FDXMS does not itself permanently alter the mode.

Correct: FDXMS does not permanently...
Incorrect: You do not load DPMI as a driver normally. Programs load it
at runtime. However... see the DOS box discussion below.
Incorrect: You do not need VCPI to reach protected mode from real mode.
You need it to reach protected mode from v86 mode. Most protected mode
programs know how to reach protected mode from real mode. They only need
VCPI when they are locked in v86 mode. See DOS box discussion, too.
Correction: Only emm386-like programs offer VCPI, as only those lock DOS
in v86 mode. HIMEM and FDXMS do not do this so they do not offer VCPI.

> So then...hmmm  as Eric was saying  I guess if you load FDXMS first, and 
> then emm386, FDXMS would not get pushed around by emm386.  But if FDXMS 
> was loaded afterward, emm386 would put it into some mode(V86 real or 
> protected?)  So I guess it's best to load FDXMS first!  :-)

Incorrect: You cannot load an XMS driver after an EMS driver.
Halfcorrect: An EMS driver drags the whole DOS into v86 mode, which may
harm XMS drivers. Especially if the EMS driver supports less RAM than the XMS
driver does - the rest will then just be left behind and gone in v86 mode!!!
Halfcorrect: Most EMS drivers (exception: DR-DOS emm386) *require* an XMS
driver to be loaded before you can load them (the XMS driver helps with A20).

> I should also correct myself:  While most of us here I suppose are not 
> that concerned with running DOS boxes in Windows, we may indeed be 
> running DOS boxes in Linux, in which there might be multiple DOS boxes 
> running in that system.  So then a DPMI would be of importance to us 
> after all...

Wrong. In DOS boxes (both Linux and Windows), DPMI is permanently available
to the DOS programs. So they do not need any driver for it, nor do they
need VCPI. Drivers for EMS and XMS are also directly provided by Linux and
Windows, so nothing to worry about for FreeDOS.
Some programs do not want DPMI but full VCPI or real mode control over the
system. Linux and Windows cannot allow this, and there is nothing FreeDOS
needs to do about it or could do about it. If you need full control, you
need to run Bochs or VMware or really boot DOS. You cannot have this in a
stock DOS box as the Windows or Linux one.

Eric