<s>
The	O
ZX	B-Device
Interface	I-Device
2	I-Device
is	O
a	O
peripheral	O
from	O
Sinclair	O
Research	O
for	O
its	O
ZX	B-Operating_System
Spectrum	I-Operating_System
home	O
computer	O
released	O
in	O
September	O
1983	O
.	O
</s>
<s>
It	O
has	O
two	O
joystick	B-Device
ports	O
and	O
a	O
ROM	B-Protocol
cartridge	I-Protocol
slot	O
,	O
which	O
offers	O
instant	O
loading	O
times	O
.	O
</s>
<s>
The	O
joystick	B-Device
ports	O
are	O
not	O
compatible	O
with	O
the	O
popular	O
Kempston	B-Device
interface	I-Device
,	O
and	O
thus	O
do	O
not	O
work	O
with	O
most	O
Spectrum	O
games	O
released	O
prior	O
to	O
the	O
launch	O
of	O
the	O
ZX	B-Device
Interface	I-Device
2	I-Device
.	O
</s>
<s>
Availability	O
of	O
cartridge	B-Protocol
software	O
is	O
very	O
limited	O
:	O
The	O
cost	O
was	O
almost	O
twice	O
as	O
much	O
as	O
the	O
same	O
game	O
on	O
cassette	B-Device
tape	I-Device
,	O
and	O
each	O
cartridge	B-Protocol
can	O
only	O
hold	O
16	O
KiB	O
,	O
making	O
it	O
almost	O
immediately	O
obsolete	O
as	O
the	O
majority	O
of	O
Spectrums	O
sold	O
were	O
48K-models	O
,	O
which	O
the	O
software	O
publishers	O
targeted	O
.	O
</s>
<s>
Paul	O
Farrow	O
has	O
demonstrated	O
that	O
it	O
is	O
possible	O
to	O
produce	O
custom	O
ROM	B-Protocol
cartridges	I-Protocol
,	O
including	O
the	O
ability	O
to	O
exceed	O
the	O
16	O
KiB	O
design	O
limitation	O
of	O
the	O
ROM	B-Protocol
cartridges	I-Protocol
.	O
</s>
<s>
The	O
interface	O
two	O
comes	O
with	O
two	O
joystick	B-Device
ports	O
that	O
(	O
unlike	O
the	O
Kempston	O
which	O
used	O
the	O
IN31	O
command	O
)	O
are	O
mapped	O
to	O
actual	O
key	O
presses	O
.	O
</s>
<s>
Joystick	B-Device
interfaces	O
that	O
mapped	O
to	O
the	O
cursor	O
keys	O
are	O
available	O
,	O
but	O
like	O
the	O
popular	O
Kempston	B-Device
interface	I-Device
they	O
are	O
limited	O
to	O
supporting	O
a	O
single	O
joystick	B-Device
only	O
.	O
</s>
<s>
It	O
is	O
the	O
twin	O
joystick	B-Device
feature	O
of	O
the	O
ZX	B-Device
Interface	I-Device
2	I-Device
that	O
turned	O
out	O
to	O
be	O
its	O
major	O
selling	O
point	O
.	O
</s>
