Hi Eric,

>         in case you used an USB mouse with BIOS PS/2 over USB
>         support: Try a PS/2 mouse or a DOS USB driver instead of
>         "BIOS legacy".

My mouse is not USB. It is a real old one, with a flat plug with
two rows of holes.

> >         4. Holding down keyboard keys while screen refreshes, as
> >            suggested by Larry (doc...@yahoo.com): shift, ctrl and
> >            alt keys cut screen refreshing time by half.
> >            Right-hand alt key is even slightly better.

>         Why does that make a difference?

I have no idea why it makes a difference. I can only say that,
for the drawing used for tests, the screen normally refreshes in
about 10 sec, but will refresh in 5 sec if either shift, ctrl or
alt is held down.

>         Did you try FDAPM ADV:REG instead of FDAPM APMDOS?

I can try it, but as far as screen refreshing speed is concerned,
option APMbios seems good enough: it is as fast as if FDAPM was
not loaded.

> >         Methods 4 and 5 are cumulative, i.e., refresh time is
> >         reduced to one-quarter of the original time if both are
> >         used. This is a substantial improvement, but still a long
> >         way away from the speed of MS-DOS.

>         How big is the difference? Does the MS kernel matter, the
>         MS mouse driver or both?

These are the differences observed under FreeDOS:

  -- Method 5 (avoiding option APMDOS for FDAPM) by itself
     reduces screen refreshing time from 10 to 5 sec.

  -- Method 4 (holding down keys) by itself also reduces it from
     10 to 5 sec.

  -- Methods 4 and 5 in combination reduce it from 10 to 2.5
     sec, i.e., both have their effect.

The mouse driver does not seem to matter: speed is the same with
either CuteMouse or Logitech driver.

Please explain what "MS kernel" is. Is it a file in Microsoft
DOS, like the one in FreeDOS? Anyway, tests with MS-DOS were done
with version 6.22, installed from original floppies.

Here is a summary of the whole thing:

  - Under FreeDOS, refresh speed is increased by avoiding FDAPM
    with option APMDOS. It can be further increased in two ways:
    by holding down keys or, much better, by moving the mouse.

  - Under MS-DOS, refresh speed is much faster than any of the



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