<s>
DTACK	B-Architecture
Grounded	I-Architecture
was	O
a	O
computer	O
hobbyist	O
newsletter	O
published	O
from	O
July	O
1981	O
to	O
September	O
1985	O
by	O
Hal	O
W	O
.	O
Hardenberg	O
.	O
</s>
<s>
Subtitled	O
"	O
The	O
Journal	O
of	O
Simple	O
68000	B-Device
Systems	O
"	O
,	O
the	O
newsletter	O
was	O
dedicated	O
to	O
the	O
proposition	O
that	O
the	O
Motorola	B-Device
68000	I-Device
CPU	O
could	O
be	O
used	O
to	O
build	O
simple	O
,	O
fast	O
computers	O
.	O
</s>
<s>
This	O
was	O
before	O
68000-based	O
personal	O
computers	O
like	O
the	O
Sharp	B-Device
X68000	I-Device
,	O
Macintosh	B-Device
,	O
Amiga	B-Device
,	O
and	O
Atari	B-Device
ST	I-Device
had	O
been	O
created	O
.	O
</s>
<s>
In	O
1981	O
Motorola	O
was	O
marketing	O
the	O
68000	B-Device
solely	O
as	O
a	O
CPU	O
for	O
Unix	O
workstations	O
.	O
</s>
<s>
Hal	O
believed	O
that	O
the	O
68000	B-Device
could	O
be	O
used	O
as	O
a	O
simple	O
embedded	O
microprocessor	O
as	O
well	O
,	O
and	O
used	O
the	O
newsletter	O
to	O
explain	O
how	O
to	O
do	O
that	O
.	O
</s>
<s>
The	O
ostensible	O
purpose	O
of	O
the	O
newsletter	O
was	O
to	O
promote	O
Hal	O
's	O
company	O
's	O
line	O
of	O
68000-based	O
hardware	O
and	O
software	O
.	O
</s>
<s>
"	O
DTACK	O
"	O
is	O
the	O
name	O
of	O
a	O
pin	O
on	O
the	O
Motorola	B-Device
68000	I-Device
CPU	O
that	O
informs	O
the	O
CPU	O
that	O
data	O
is	O
ready	O
to	O
be	O
read	O
from	O
memory	O
.	O
</s>
<s>
(	O
The	O
68000	B-Device
has	O
no	O
separate	O
I/O	O
address	O
space	O
,	O
so	O
all	O
I/O	O
devices	O
must	O
be	O
memory-mapped	O
.	O
)	O
</s>
<s>
Therefore	O
,	O
typically	O
only	O
relatively	O
simple	O
systems	O
can	O
use	O
a	O
design	O
with	O
"	O
DTACK	B-Architecture
grounded	I-Architecture
"	O
(	O
i.e.	O
,	O
DTACK	O
always	O
asserted	O
)	O
.	O
</s>
<s>
When	O
many	O
different	O
peripherals	O
with	O
different	O
maximum	O
speed	O
capabilities	O
must	O
be	O
used	O
in	O
a	O
small	O
system	O
,	O
another	O
solution	O
to	O
keep	O
DTACK	B-Architecture
grounded	I-Architecture
is	O
to	O
slow	O
down	O
the	O
clock	O
rate	O
of	O
the	O
CPU	O
so	O
that	O
all	O
memory	O
and	O
peripheral	O
devices	O
can	O
transfer	O
data	O
at	O
the	O
(	O
reduced	O
)	O
maximum	O
speed	O
of	O
the	O
CPU	O
.	O
</s>
<s>
Many	O
other	O
microprocessors	O
,	O
including	O
the	O
Intel	B-General_Concept
8086	I-General_Concept
,	O
8088	B-Device
,	O
80286	B-General_Concept
,	O
80386	B-General_Concept
,	O
8080	B-General_Concept
,	O
8085	B-General_Concept
,	O
Zilog	B-General_Concept
Z80	I-General_Concept
,	O
and	O
6502	B-General_Concept
family	I-General_Concept
,	O
each	O
have	O
an	O
input	O
pin	O
that	O
serves	O
a	O
similar	O
function	O
to	O
DTACK	O
,	O
but	O
it	O
is	O
usually	O
named	O
READY	O
or	O
RDY	O
.	O
</s>
<s>
(	O
On	O
the	O
Z80	B-General_Concept
,	O
it	O
is	O
named	O
WAIT	O
.	O
)	O
</s>
<s>
Therefore	O
,	O
a	O
reference	O
to	O
DTACK	O
distinctively	O
implies	O
the	O
68000	B-Device
family	O
of	O
CPUs	O
.	O
</s>
<s>
In	O
order	O
to	O
discourage	O
photocopying	O
of	O
the	O
newsletter	O
,	O
a	O
portion	O
of	O
the	O
DTACK	B-Architecture
Grounded	I-Architecture
newsletter	O
was	O
printed	O
on	O
dark	O
red	O
paper	O
.	O
</s>
<s>
Hal	O
produced	O
a	O
fast	O
Basic	O
interpreter	O
for	O
the	O
Atari	B-Device
ST	I-Device
computer	O
.	O
</s>
<s>
But	O
it	O
was	O
non-standard	O
:	O
it	O
could	O
n't	O
run	O
Microsoft	B-Language
BASIC	I-Language
programs	O
,	O
and	O
it	O
could	O
n't	O
read	O
or	O
write	O
MS-DOS	B-Application
format	O
floppy	O
disks	O
.	O
</s>
<s>
In	O
the	O
1990s	O
,	O
Hal	O
revived	O
DTACK	B-Architecture
Grounded	I-Architecture
as	O
an	O
occasional	O
column	O
in	O
Dr.	O
Dobb	O
's	O
Journal	O
called	O
"	O
DTACK	O
Revisited	O
"	O
.	O
</s>
