<s>
WHDLoad	B-Device
is	O
a	O
software	O
package	O
for	O
the	O
Amiga	B-Device
platform	I-Device
to	O
make	O
installation	O
of	O
software	O
to	O
a	O
hard	B-Device
disk	I-Device
easier	O
,	O
for	O
such	O
things	O
as	O
demos	O
or	O
games	O
.	O
</s>
<s>
Allowing	O
for	O
better	O
compatibility	B-General_Concept
for	O
Amiga	B-Device
software	O
,	O
which	O
can	O
sometimes	O
have	O
hardware	O
incompatibilities	O
making	O
them	O
hard	O
to	O
use	O
in	O
emulated	B-Application
environments	O
due	O
to	O
the	O
widely	O
varying	O
hardware	O
specifications	O
of	O
the	O
Amiga	B-Device
product	O
line	O
across	O
its	O
history	O
.	O
</s>
<s>
WHDLoad	B-Device
basically	O
circumvents	O
the	O
operating	O
system	O
in	O
the	O
Amiga	B-Device
for	O
greater	O
compatibility	B-General_Concept
and	O
preserves	O
the	O
original	O
program	O
environment	O
.	O
</s>
<s>
WHDLoad	B-Device
makes	O
it	O
possible	O
to	O
autostart	O
an	O
installed	O
floppy	B-Device
disk	I-Device
image	O
by	O
clicking	O
an	O
icon	O
.	O
</s>
<s>
Two	O
special	O
parts	O
are	O
required	O
,	O
each	O
one	O
specially	O
written	O
for	O
the	O
client	O
program	O
:	O
To	O
install	O
media	O
,	O
it	O
must	O
be	O
read	O
from	O
the	O
original	O
disk	O
and	O
written	O
to	O
an	O
image	O
file	O
on	O
the	O
hard	B-Device
drive	I-Device
by	O
the	O
"	O
Imager	O
"	O
.	O
</s>
<s>
The	O
"	O
Slave	O
"	O
interface	O
allows	O
interaction	O
between	O
the	O
program	O
and	O
WHDLoad	B-Device
,	O
and	O
co-ordinates	O
the	O
reading	O
and	O
writing	O
of	O
files	O
.	O
</s>
<s>
This	O
makes	O
it	O
possible	O
to	O
run	O
or	O
emulate	O
programs	O
that	O
are	O
traditionally	O
incompatible	O
with	O
common	O
emulators	B-Application
such	O
as	O
WinFellow	B-Application
,	O
or	O
WinUAE	B-Device
.	O
</s>
<s>
WHDLoad	B-Device
can	O
be	O
easier	O
to	O
use	O
than	O
trying	O
to	O
figure	O
out	O
the	O
exact	O
configuration	O
for	O
the	O
aforementioned	O
emulators	B-Application
as	O
well	O
.	O
</s>
<s>
The	O
primary	O
reason	O
for	O
this	O
loader	O
is	O
that	O
a	O
large	O
number	O
of	O
computer	O
games	O
for	O
the	O
Amiga	B-Device
do	O
n't	O
properly	O
interact	O
with	O
the	O
AmigaOS	B-Application
operating	O
system	O
,	O
but	O
instead	O
run	O
directly	O
on	O
the	O
Amiga	B-Device
hardware	O
,	O
making	O
assumptions	O
about	O
specific	O
control	O
registers	B-General_Concept
,	O
memory	O
locations	O
,	O
etc	O
.	O
</s>
<s>
The	O
hardware	O
of	O
newer	O
Amiga	B-Device
models	I-Device
had	O
been	O
greatly	O
revised	O
,	O
causing	O
these	O
assumptions	O
to	O
break	O
when	O
trying	O
to	O
run	O
the	O
same	O
games	O
on	O
newer	O
hardware	O
,	O
and	O
vice	O
versa	O
with	O
newer	O
games	O
on	O
older	O
hardware	O
.	O
</s>
<s>
WHDLoad	B-Device
provides	O
a	O
way	O
to	O
install	O
such	O
games	O
on	O
an	O
AmigaOS-compatible	O
hard	B-Device
drive	I-Device
and	O
run	O
on	O
newer	O
hardware	O
.	O
</s>
<s>
An	O
added	O
benefit	O
is	O
the	O
avoidance	O
of	O
loading	O
times	O
and	O
disk	O
swaps	O
,	O
because	O
everything	O
the	O
game	O
needs	O
is	O
stored	O
on	O
the	O
hard	B-Device
drive	I-Device
.	O
</s>
<s>
The	O
first	O
public	O
release	O
of	O
WHDLoad	B-Device
was	O
on	O
September	O
5	O
,	O
1996	O
,	O
and	O
the	O
latest	O
available	O
version	O
is	O
18.8	O
released	O
in	O
May	O
2022	O
.	O
</s>
<s>
WHDLoad	B-Device
takes	O
over	O
the	O
entire	O
operating	O
system	O
which	O
may	O
cause	O
problems	O
with	O
some	O
software	O
(	O
e.g.	O
</s>
<s>
WHDLoad	B-Device
games	O
are	O
stored	O
on	O
the	O
AmigaOS	B-Application
file	O
system	O
as	O
disk	B-Application
images	I-Application
,	O
relying	O
on	O
driver	O
files	O
known	O
as	O
"	O
WHDLoad	B-Device
slaves	O
"	O
to	O
work	O
.	O
</s>
<s>
These	O
slave	O
files	O
are	O
freely	O
available	O
from	O
the	O
Internet	O
(	O
as	O
Freeware	B-License
)	O
,	O
but	O
the	O
games	O
themselves	O
have	O
to	O
be	O
acquired	O
separately	O
,	O
to	O
prevent	O
software	O
piracy	O
.	O
</s>
<s>
Additionally	O
,	O
many	O
fans	O
have	O
made	O
their	O
own	O
freeware	B-License
games	O
,	O
which	O
are	O
also	O
freely	O
,	O
and	O
legally	O
,	O
available	O
.	O
</s>
<s>
The	O
WHDLoad	B-Device
"	O
Slave	O
"	O
interface	O
is	O
integrated	O
into	O
the	O
OS	O
in	O
such	O
way	O
that	O
one	O
can	O
double-click	O
a	O
program	O
icon	O
to	O
run	O
the	O
program	O
at	O
any	O
time	O
.	O
</s>
<s>
When	O
the	O
user	O
executes	O
the	O
program	O
,	O
by	O
clicking	O
a	O
stored	O
image	O
icon	O
,	O
the	O
AmigaOS	B-Application
operating	O
system	O
loads	O
the	O
WHDLoad	B-Device
executable	B-Application
and	O
starts	O
it	O
.	O
</s>
<s>
If	O
the	O
Preload	O
feature	O
is	O
enabled	O
into	O
the	O
requester	O
page	O
of	O
WHDLoad	B-Device
,	O
then	O
the	O
program	O
attempts	O
to	O
load	O
disk	B-Application
images	I-Application
and	O
files	O
into	O
RAM	O
(	O
insofar	O
as	O
free	O
memory	O
is	O
available	O
)	O
.	O
</s>
<s>
At	O
this	O
point	O
WHDLoad	B-Device
performs	O
its	O
main	O
task	O
of	O
switching	O
off	O
the	O
AmigaOS	B-Application
operating	O
system	O
,	O
disables	O
multitasking	B-Operating_System
and	O
interrupts	B-Application
,	O
and	O
copies	O
memory	O
regions	O
which	O
are	O
used	O
by	O
AmigaOS	B-Application
and	O
required	O
by	O
the	O
installed	O
program	O
to	O
an	O
unused	O
place	O
until	O
the	O
AmigaOS	B-Application
is	O
needed	O
again	O
.	O
</s>
<s>
WHDLoad	B-Device
also	O
degrades	O
the	O
graphics	O
hardware	O
to	O
OCS	B-Device
on	O
original	O
Amiga	B-Device
machines	O
(	O
this	O
function	O
actually	O
can	O
work	O
also	O
on	O
emulated	B-Application
Amigas	B-Device
,	O
but	O
only	O
on	O
newer	O
versions	O
of	O
WinUAE	B-Device
which	O
recognizes	O
WHDLoad	B-Device
and	O
preserves	O
its	O
interrupts	B-Application
)	O
,	O
then	O
WHDLoad	B-Device
initializes	O
all	O
hardware	O
with	O
defined	O
values	O
and	O
jumps	O
into	O
the	O
Slave	O
interface	O
required	O
for	O
the	O
program	O
in	O
question	O
.	O
</s>
<s>
The	O
Slave	O
interface	O
loads	O
the	O
main	O
executable	B-Application
of	O
the	O
installed	O
program	O
by	O
calling	O
a	O
WHDLoad	B-Device
function	O
(	O
resload_DiskLoad	O
or	O
resload_LoadFile	O
)	O
,	O
then	O
patches	O
the	O
main	O
executable	B-Application
(	O
so	O
that	O
the	O
loaded	O
program	O
will	O
be	O
capable	O
of	O
loading	O
its	O
data	O
stored	O
into	O
the	O
hard	B-Device
disk	I-Device
via	O
the	O
Slave	O
,	O
in	O
order	O
to	O
fix	O
compatibility	B-General_Concept
problems	O
,	O
and	O
to	O
enable	O
an	O
exit	O
from	O
the	O
program	O
)	O
and	O
calls	O
the	O
main	O
executable	B-Application
.	O
</s>
<s>
At	O
this	O
point	O
,	O
the	O
program	O
that	O
has	O
been	O
installed	O
can	O
perform	O
the	O
task	O
for	O
which	O
it	O
has	O
been	O
written	O
,	O
loading	O
its	O
data	O
as	O
it	O
would	O
from	O
a	O
real	O
floppy	B-Device
disk	I-Device
.	O
</s>
<s>
When	O
this	O
action	O
is	O
performed	O
,	O
then	O
the	O
Slave	O
interface	O
returns	O
to	O
WHDLoad	B-Device
by	O
calling	O
a	O
resload_Abort	O
internal	O
function	O
.	O
</s>
<s>
The	O
OS	O
will	O
be	O
restored	O
with	O
all	O
hardware	O
registers	B-General_Concept
and	O
original	O
display	O
.	O
</s>
<s>
A	O
standard	O
Amiga	B-Application
1200	I-Application
or	O
Amiga	B-Device
600	I-Device
without	O
any	O
extra	O
memory	O
,	O
will	O
only	O
work	O
with	O
a	O
limited	O
number	O
of	O
games	O
.	O
</s>
<s>
Which	O
usually	O
means	O
games	O
using	O
OCS/ECS	O
and	O
one	O
floppy	B-Device
disk	I-Device
.	O
</s>
<s>
It	O
is	O
recommended	O
to	O
install	O
either	O
a	O
or	O
RAM	O
Board	O
in	O
the	O
trapdoor	O
slot	O
to	O
ensure	O
compatibility	B-General_Concept
for	O
99%	O
of	O
the	O
games	O
.	O
</s>
<s>
A	O
harddisk	B-Device
is	O
required	O
,	O
the	O
number	O
of	O
games	O
that	O
can	O
be	O
installed	O
depend	O
on	O
the	O
size	O
of	O
the	O
harddisk	B-Device
.	O
</s>
