Mikael Kjellstr”m wrote in a message to Mike Bilow:

 > MK> Someone who knows why?  And is it going to be fixed in time
 > MK> for Merlin?  Or maybe it isn't fixable?
 >
 > Try "DIR C:\ /S > NUL" and you will not see any
jerkiness in the mouse.
 > What is happening is that the mouse movements are being processed by the
 > operating system, but the screen cannot be updated quickly enough to show
 > it.  Updating the mouse cursor is, I believe, handled by a separare
 > thread in PM.

 MK> Yes, I know.  So if one could change the priority for the
 MK> mouse-thread then the jerkiness would go away?  And why
 MK> isn't the mouse set to time critical in the first place?

I really don't think that the mouse should be considered time critical.

 MK> And when the scrolling is going on the other programs gets
 MK> no or close to no cpu at all.  I made a PM-program that has
 MK> at thread that updates a counter and it stops completly when
 MK> the scrolling is occuring.  But when I changed the update
 MK> thread in my program to timecritical it got cpu OK. So there
 MK> is something else going on here.  Is the scrolling set to
 MK> timeritical for DOS and OS/2-windows? 

Scrolling is handled inside the presentation device drivers.  There is a
good reason for this, since many video boards these days have the
capability of accelerating common operations such as scrolling in hardware.
 Unfortunately, a side effect of this is that device drivers are never
pre-empted by the scheduler without their explicit yield, so scrolling
operates by default at apparent high priority.

 MK> And it's just those DOS and OS/2-windows that gets this
 MK> effect.  I don't have the same problem when scrolling for
 MK> example an E.EXE window. 

PM itself handles scrolling differently than text scrolling.  This is again
an issue for the display driver internals.

 MK> Maybe something with the VIO-subsystem?

 MK> Many questions and guesses now :-)

If you use a video board with an S3 chip, it will scroll text so fast that
you will no longer care about its priority.
 
-- Mike


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