<s>
The	O
TK90X	B-Device
was	O
a	O
Brazilian	O
ZX	B-Operating_System
Spectrum	I-Operating_System
clone	O
made	O
in	O
1985	O
by	O
Microdigital	O
Electrônica	O
,	O
a	O
company	O
from	O
São	O
Paulo	O
,	O
that	O
had	O
previously	O
manufactured	O
ZX80	B-Operating_System
(	O
TK80	O
,	O
TK82	O
)	O
and	O
ZX81	O
clones	O
(	O
TK82C	B-Device
,	O
TK83	O
and	O
TK85	B-Device
)	O
.	O
</s>
<s>
Reported	O
TK90X	B-Device
sales	O
in	O
October	O
1986	O
were	O
2500	O
machines	O
per	O
month	O
.	O
</s>
<s>
The	O
case	O
was	O
a	O
little	O
taller	O
than	O
the	O
original	O
Spectrum	O
and	O
the	O
keyboard	O
placement	O
was	O
equal	O
to	O
the	O
original	O
keyboard	O
,	O
except	O
for	O
some	O
additional	O
Sinclar	B-Language
BASIC	I-Language
commands	O
that	O
did	O
not	O
exist	O
in	O
the	O
Spectrums	O
(	O
UDG	O
for	O
user	O
defined	O
characters	O
in	O
the	O
place	O
of	O
the	O
£	O
sign	O
-	O
including	O
specific	O
Portuguese	O
and	O
Spanish	O
characters	O
such	O
as	O
and	O
,	O
as	O
well	O
as	O
accented	O
vowels	O
-	O
and	O
the	O
Trace	O
function	O
)	O
.	O
</s>
<s>
There	O
were	O
two	O
versions	O
of	O
the	O
machine	O
,	O
with	O
16KB	O
and	O
48KB	O
of	O
RAM	B-Architecture
.	O
</s>
<s>
They	O
contained	O
the	O
same	O
Z80A	B-General_Concept
processor	O
running	O
at	O
3.58MHz	O
,	O
a	O
ROM	B-Device
chip	I-Device
,	O
and	O
RAM	B-Architecture
chips	I-Architecture
(	O
dynamic	O
RAMs	B-Architecture
4116	O
and	O
4416	O
)	O
.	O
</s>
<s>
Microdigital	O
reverse	O
engineered	O
a	O
CMOS	B-Device
integrated	O
circuit	O
(	O
IC	O
)	O
with	O
similar	O
functionality	O
to	O
the	O
original	O
Bipolar	O
IC	O
ULA	O
from	O
Sinclair/Ferranti	O
.	O
</s>
<s>
The	O
TV	O
modulator	O
was	O
tuned	O
to	O
VHF	B-Algorithm
channel	O
3	O
,	O
with	O
the	O
TV	O
standard	O
being	O
hardware	O
selectable	O
to	O
PAL-M	O
(	O
60Hz	O
)	O
as	O
used	O
in	O
Brazil	O
,	O
PAL-N	O
(	O
50Hz	O
)	O
as	O
used	O
in	O
Uruguay	O
,	O
Argentina	O
and	O
Paraguay	O
and	O
NTSC	O
(	O
60Hz	O
)	O
as	O
used	O
in	O
USA	O
and	O
many	O
other	O
countries	O
.	O
</s>
<s>
An	O
improvement	O
over	O
the	O
original	O
ZX	B-Operating_System
Spectrum	I-Operating_System
was	O
the	O
sound	O
output	O
via	O
modulated	O
RF	O
direct	O
to	O
the	O
TV	O
set	O
instead	O
of	O
the	O
beeper	O
.	O
</s>
<s>
Most	O
software	O
written	O
for	O
the	O
Spectrum	O
ran	O
on	O
the	O
TK90X	B-Device
,	O
with	O
some	O
minor	O
incompatibilities	O
.	O
</s>
<s>
disk	O
drive	O
interface	O
 '	O
(	O
with	O
a	O
printer	O
interface	O
included	O
)	O
and	O
'	O
IDS91	O
 '	O
(	O
with	O
a	O
printer	O
interface	O
included	O
made	O
by	O
Synchron	O
)	O
or	O
'	O
IDS2001ne	O
 '	O
(	O
these	O
exclusively	O
compatible	O
only	O
with	O
the	O
TK90X	B-Device
or	O
TK95	B-Device
{	O
no	O
ZX	B-Operating_System
Spectrum	I-Operating_System
use	O
possible}	O
,	O
also	O
from	O
Synchron	O
,	O
and	O
also	O
with	O
a	O
printer	O
interface	O
included	O
)	O
.	O
</s>
<s>
The	O
TK90X	B-Device
was	O
replaced	O
by	O
the	O
TK95	B-Device
,	O
which	O
had	O
a	O
different	O
keyboard	O
(	O
professional	O
)	O
and	O
case	O
(	O
identical	O
to	O
the	O
Commodore	B-Operating_System
Plus4	I-Operating_System
)	O
and	O
exactly	O
the	O
same	O
circuit	O
board	O
and	O
schematics	O
.	O
</s>
<s>
The	O
motherboard	O
was	O
marked	O
as	O
TK90X	B-Device
.	O
</s>
<s>
The	O
unit	O
had	O
a	O
few	O
differences	O
in	O
the	O
ROM	B-Device
that	O
made	O
the	O
TK95	B-Device
more	O
compatible	O
with	O
the	O
original	O
ZX	B-Operating_System
Spectrum	I-Operating_System
.	O
</s>
<s>
It	O
used	O
the	O
same	O
ULA	O
chip	O
,	O
with	O
only	O
digital	O
logic	O
ports	O
and	O
the	O
analogue	O
part	O
outside	O
the	O
ULA	O
chip	O
,	O
exactly	O
as	O
in	O
the	O
TK90X	B-Device
.	O
</s>
<s>
It	O
was	O
reported	O
that	O
the	O
TK95	B-Device
provided	O
more	O
compatibility	O
with	O
the	O
original	O
ZX	B-Operating_System
Spectrum	I-Operating_System
(	O
e.g.	O
,	O
the	O
game	O
Mikie	B-Application
runs	O
only	O
on	O
the	O
TK95	B-Device
,	O
not	O
on	O
the	O
TK90X	B-Device
.	O
</s>
<s>
the	O
D1	O
diode	O
was	O
disconnected	O
and	O
some	O
changes	O
to	O
the	O
ROM	B-Device
were	O
made	O
)	O
.	O
</s>
<s>
TK90X	B-Device
users	O
in	O
Brazil	O
used	O
to	O
make	O
a	O
switch	O
to	O
choose	O
the	O
original	O
TK90X	B-Device
(	O
or	O
TK95	B-Device
)	O
ROM	B-Device
or	O
the	O
ZX	B-Operating_System
Spectrum	I-Operating_System
ROM	B-Device
internally	O
,	O
so	O
they	O
could	O
use	O
almost	O
all	O
of	O
the	O
Spectrum	O
's	O
software	O
.	O
</s>
<s>
During	O
that	O
period	O
,	O
Brazilians	O
were	O
not	O
allowed	O
to	O
import	O
computers	O
and	O
therefore	O
the	O
TK90X	B-Device
became	O
the	O
first	O
affordable	O
color	O
computer	O
for	O
Brazilians	O
.	O
</s>
<s>
It	O
was	O
successful	O
in	O
other	O
Latin	O
America	O
countries	O
,	O
such	O
as	O
Uruguay	O
and	O
Argentina	O
,	O
but	O
the	O
export	O
model	O
used	O
a	O
different	O
circuit	O
board	O
and	O
schematics	O
,	O
and	O
an	O
original	O
Ferranti	O
ULA	O
from	O
the	O
ZX	B-Operating_System
Spectrum	I-Operating_System
.	O
</s>
<s>
Because	O
of	O
its	O
affordability	O
,	O
many	O
commercial	O
software	O
programs	O
were	O
locally	O
developed	O
for	O
the	O
first	O
time	O
for	O
use	O
of	O
small	O
businesses	O
in	O
Latin	O
America	O
to	O
run	O
on	O
the	O
TK90X	B-Device
and	O
millions	O
of	O
users	O
had	O
their	O
first	O
computer	O
experience	O
with	O
it	O
.	O
</s>
<s>
There	O
's	O
an	O
active	O
user	O
base	O
of	O
enthusiasts	O
of	O
this	O
computer	O
,	O
with	O
dedicated	O
websites	O
discussing	O
software	O
preservation	O
,	O
peripherals	O
and	O
homebrew	B-Application
development	O
and	O
modifications	O
.	O
</s>
