6.2 "Disk-Video" Modes
These "video modes" do not involve a video adapter at all. They use (in
order or preference) your expanded memory, your extended memory, or your
disk drive (as file FRACTINT.$$$) to store the fractal image. These
modes are useful for creating images beyond the capacity of your video
adapter right up to the current internal limit of 32767 x 32767 x 256,
e.g. for subsequent printing. They're also useful for background
processing under multi-tasking DOS managers - create an image in a disk-
video mode, save it, then restore it in a real video mode.
While you are using a disk-video mode, your screen will display text
information indicating whether memory or your disk drive is being used,
and what portion of the "screen" is being read from or written to. A
"Cache size" figure is also displayed. 64K is the maximum cache size.
If you see a number less than this, it means that you don't have a lot
of memory free, and that performance will be less than optimum. With a
very low cache size such as 4 or 6k, performance gets considerably worse
in cases using solid guessing, boundary tracing, plasma, or anything
else which paints the screen non-linearly. If you have this problem,
all we can suggest is having fewer TSR utilities loaded before starting
Fractint, or changing in your config.sys file, such as reducing a very
high BUFFERS value.
The zoom box is disabled during disk-video modes (you couldn't see where
it is anyway). So is the orbit display feature.
Color Cycling (p. 23) can be used during disk-video modes, but only to
load or save a color palette.
When using real disk for your disk-video, Fractint previously would not
generate some "attractor" types (e.g. Lorenz) nor "IFS" images. These
stress disk drives with intensive reads and writes, but with the caching
algorithm performance may be acceptable. Currently Fractint gives you a
warning message but lets you proceed. You can end the calculation with
<Esc> if you think your hard disk is getting too strenuous a workout.
When using a real disk, and you are not directing the file to a RAM
disk, and you aren't using a disk caching program on your machine,
specifying BUFFERS=10 (or more) in your config.sys file is best for
performance. BUFFERS=10,2 or even BUFFERS=10,4 is also good. It is
also best to keep your disk relatively "compressed" (or "defragmented")
if you have a utility to do this.
In order to use extended memory, you must have HIMEM.SYS or an
equivalent that supports the XMS 2.0 standard or higher. Also, you
can't have a VDISK installed in extended memory. Himem.sys is
distributed with Microsoft Windows 286/386 and 3.0. If you have
problems using the extended memory, try rebooting with just himem.sys
loaded and see if that clears up the problem.
If you are running background disk-video fractals under Windows 3, and
you don't have a lot of real memory (over 2Mb), you might find it best
to force Fractint to use real disk for disk-video modes. (Force this by
using a .pif file with extended memory and expanded memory set to zero.)
Try this if your disk goes crazy when generating background images,
which are supposedly using extended or expanded memory. This problem
can occur because, to multi-task, sometimes Windows must page an
application's expanded or extended memory to disk, in big chunks.
Fractint's own cached disk access may be faster in such cases.