<s>
Rekursiv	B-General_Concept
was	O
a	O
computer	O
processor	O
designed	O
by	O
David	O
M	O
.	O
Harland	O
in	O
the	O
mid-1980s	O
at	O
a	O
division	O
of	O
hi-fi	O
manufacturer	O
Linn	O
Products	O
.	O
</s>
<s>
It	O
was	O
one	O
of	O
the	O
few	O
computer	B-General_Concept
architectures	I-General_Concept
intended	O
to	O
implement	O
object-oriented	B-Language
concepts	O
directly	O
in	O
hardware	O
,	O
a	O
form	O
of	O
high-level	B-Architecture
language	I-Architecture
computer	I-Architecture
architecture	I-Architecture
.	O
</s>
<s>
The	O
Rekursiv	B-General_Concept
operated	O
directly	O
on	O
objects	O
rather	O
than	O
bits	O
,	O
nibbles	O
,	O
bytes	B-Application
and	O
words	O
.	O
</s>
<s>
Virtual	B-Architecture
memory	I-Architecture
was	O
used	O
as	O
a	O
persistent	O
object	O
store	O
and	O
unusually	O
,	O
the	O
processor	O
instruction	B-General_Concept
set	I-General_Concept
supported	O
recursion	O
(	O
hence	O
the	O
name	O
)	O
.	O
</s>
<s>
By	O
the	O
time	O
the	O
project	O
had	O
delivered	O
its	O
first	O
implementation	O
,	O
new	O
processors	O
like	O
the	O
Sun	B-Architecture
SPARC	I-Architecture
and	O
Intel	B-General_Concept
486	I-General_Concept
had	O
surpassed	O
its	O
performance	O
,	O
and	O
development	O
was	O
abandoned	O
in	O
1988	O
.	O
</s>
<s>
The	O
Rekursiv	B-General_Concept
project	O
started	O
as	O
an	O
effort	O
to	O
improve	O
the	O
assembly	O
line	O
controls	O
in	O
Linn	O
's	O
factories	O
in	O
Glasgow	O
,	O
Scotland	O
.	O
</s>
<s>
By	O
the	O
early	O
1980s	O
,	O
Tiefenbrun	O
had	O
become	O
convinced	O
that	O
object-oriented	B-Language
programming	I-Language
would	O
offer	O
solutions	O
to	O
these	O
problems	O
.	O
</s>
<s>
In	O
1981	O
,	O
Tiefenbrun	O
hired	O
a	O
number	O
of	O
programmers	O
to	O
write	O
a	O
version	O
of	O
the	O
seminal	O
Smalltalk	B-Application
language	O
for	O
the	O
VAX	O
systems	O
,	O
borrowing	O
some	O
syntax	O
from	O
ALGOL	B-Language
.	O
</s>
<s>
In	O
1984	O
,	O
Tiefenbrun	O
formed	O
the	O
wholly	O
owned	O
subsidiary	O
Linn	O
Smart	O
Computing	O
under	O
the	O
direction	O
of	O
University	O
of	O
Strathclyde	O
professor	O
David	O
Harland	O
and	O
the	O
Rekursiv	B-General_Concept
project	O
was	O
born	O
.	O
</s>
<s>
A	O
small	O
number	O
of	O
prototype	O
VMEbus	B-Architecture
boards	O
,	O
called	O
Hades	O
,	O
comprising	O
these	O
four	O
chips	O
plus	O
80MB	O
of	O
RAM	O
were	O
produced	O
.	O
</s>
<s>
These	O
were	O
intended	O
for	O
installation	O
in	O
a	O
host	O
system	O
such	O
as	O
a	O
Sun-3	B-Device
workstation	I-Device
.	O
</s>
<s>
Although	O
the	O
Rekursiv	B-General_Concept
was	O
never	O
fully	O
developed	O
and	O
was	O
not	O
a	O
commercial	O
success	O
,	O
several	O
Hades	O
boards	O
were	O
used	O
in	O
academic	O
research	O
projects	O
in	O
the	O
UK	O
.	O
</s>
<s>
The	O
last	O
known	O
copy	O
of	O
a	O
Rekursiv	B-General_Concept
computer	O
ended	O
up	O
at	O
the	O
bottom	O
of	O
the	O
Forth	O
and	O
Clyde	O
canal	O
in	O
Glasgow	O
.	O
</s>
<s>
According	O
to	O
a	O
post	O
by	O
a	O
researcher	O
at	O
the	O
University	O
of	O
Strathclyde	O
,	O
while	O
the	O
Rekursiv	B-General_Concept
system	O
was	O
being	O
developed	O
,	O
a	O
new	O
version	O
of	O
the	O
LINGO	O
language	O
was	O
written	O
for	O
the	O
Sun	B-Architecture
SPARC	I-Architecture
system	O
which	O
emerged	O
at	O
about	O
this	O
time	O
.	O
</s>
<s>
It	O
ran	O
twice	O
as	O
fast	O
as	O
the	O
Rekursiv	B-General_Concept
hardware	O
,	O
rendering	O
the	O
effort	O
pointless	O
.	O
</s>
<s>
The	O
underlying	O
concept	O
of	O
the	O
Rekursiv	B-General_Concept
platform	O
was	O
to	O
provide	O
a	O
hardware-assisted	O
persistent	O
object	O
store	O
,	O
constantly	O
and	O
invisibly	O
writing	O
the	O
memory	O
state	O
to	O
disk	O
without	O
intervention	O
from	O
the	O
operating	B-General_Concept
system	I-General_Concept
or	O
the	O
user	O
's	O
program	O
.	O
</s>
<s>
To	O
make	O
such	O
a	O
system	O
work	O
with	O
reasonable	O
performance	O
while	O
running	O
complex	O
programs	O
,	O
Rekursiv	B-General_Concept
was	O
designed	O
to	O
allow	O
the	O
programmer	O
to	O
write	O
their	O
own	O
instruction	B-General_Concept
set	I-General_Concept
architecture	I-General_Concept
(	O
ISA	O
)	O
dedicated	O
to	O
the	O
language	O
they	O
were	O
using	O
.	O
</s>
<s>
The	O
microcode	B-Device
instruction	B-General_Concept
set	I-General_Concept
was	O
stored	O
in	O
static	B-Architecture
RAM	I-Architecture
.	O
</s>
<s>
There	O
was	O
no	O
default	O
ISA	O
,	O
although	O
Linn	O
supplied	O
one	O
for	O
running	O
programs	O
in	O
the	O
C	B-Language
programming	I-Language
language	I-Language
.	O
</s>
<s>
Objekt	O
also	O
handled	O
the	O
mapping	O
of	O
the	O
object	O
memory	O
to	O
hard	B-Device
disk	I-Device
for	O
permanent	O
storage	O
,	O
implementing	O
a	O
virtual	B-Architecture
memory	I-Architecture
system	O
.	O
</s>
<s>
To	O
handle	O
garbage	B-General_Concept
collection	I-General_Concept
,	O
Objekt	O
divided	O
the	O
provided	O
dynamic	O
RAM	O
(	O
main	O
memory	O
)	O
into	O
two	O
halves	O
,	O
using	O
one	O
for	O
new	O
object	O
creation	O
and	O
leaving	O
the	O
other	O
unused	O
.	O
</s>
<s>
In	O
Rekursiv	B-General_Concept
,	O
the	O
addresses	O
are	O
replaced	O
by	O
40-bit	O
object	O
IDs	O
pointing	O
to	O
a	O
section	O
of	O
memory	O
allocated	O
by	O
Objekt	O
.	O
</s>
<s>
Since	O
the	O
objects	O
were	O
constantly	O
being	O
garbage	B-General_Concept
collected	I-General_Concept
,	O
many	O
of	O
these	O
values	O
might	O
point	O
to	O
non-existent	O
objects	O
,	O
meaning	O
the	O
system	O
could	O
run	O
out	O
of	O
identifiers	O
in	O
practical	O
use	O
.	O
</s>
<s>
The	O
processor	O
's	O
instruction	B-General_Concept
set	I-General_Concept
was	O
stored	O
in	O
a	O
dedicated	O
area	O
of	O
static	B-Architecture
RAM	I-Architecture
known	O
as	O
the	O
"	O
control	O
store	O
"	O
.	O
</s>
<s>
A	O
separate	O
"	O
control	O
store	O
map	O
"	O
section	O
of	O
SRAM	O
holds	O
a	O
numbered	O
table	O
of	O
entry	O
points	O
into	O
the	O
microcoded	B-Device
routines	O
,	O
mapping	O
a	O
10-bit	O
opcode	B-Language
onto	O
one	O
of	O
2,048	O
entities	O
.	O
</s>
<s>
In	O
a	O
conventional	O
processor	O
,	O
the	O
map	O
would	O
normally	O
be	O
implemented	O
in	O
hardwired	O
logic	O
in	O
the	O
opcode	B-Language
decoder	O
.	O
</s>
<s>
Opcodes	B-Language
could	O
be	O
parts	O
of	O
objects	O
and	O
stored	O
in	O
the	O
same	O
way	O
that	O
any	O
other	O
data	O
would	O
be	O
using	O
Objekt	O
.	O
</s>
<s>
For	O
performance	O
reasons	O
,	O
a	O
separate	O
memory	O
bank	O
known	O
as	O
NAM	O
(	O
and	O
NAMARG	O
)	O
reserved	O
524,288	O
40-bit	O
words	O
storing	O
10-bit	O
opcodes	B-Language
and	O
30-bit	O
arguments	O
.	O
</s>
<s>
In	O
practice	O
,	O
the	O
developer	O
of	O
a	O
programming	O
language	O
would	O
first	O
outline	O
the	O
assembler	B-Language
language	I-Language
they	O
desired	O
,	O
which	O
would	O
be	O
the	O
underlying	O
syntax	O
of	O
the	O
language	O
with	O
up	O
to	O
2,048	O
instructions	O
.	O
</s>
<s>
Commonly	O
used	O
routines	O
,	O
like	O
those	O
found	O
in	O
stdlib	B-Library
in	O
C	B-Language
,	O
would	O
then	O
be	O
coded	O
using	O
that	O
assembler	B-Language
language	I-Language
and	O
written	O
to	O
the	O
NAM	O
.	O
</s>
<s>
Simulations	O
suggested	O
that	O
Lisp	B-Language
routines	O
written	O
using	O
this	O
style	O
operated	O
about	O
20	O
times	O
faster	O
than	O
a	O
Symbolics	O
Lisp	B-Language
machine	O
.	O
</s>
<s>
The	O
company	O
also	O
produced	O
similar	O
microcode	B-Device
systems	O
for	O
Smalltalk	B-Application
and	O
Prolog	O
,	O
the	O
later	O
reducing	O
Prolog	O
's	O
complex	O
unification	O
operation	O
to	O
a	O
single	O
opcode	B-Language
.	O
</s>
<s>
The	O
Rekursiv	B-General_Concept
processor	O
consisted	O
of	O
four	O
gate-array	O
chips	O
named	O
Numerik	O
(	O
32-bit	O
ALU	B-General_Concept
)	O
,	O
Logik	O
(	O
instruction	O
sequencer	O
)	O
,	O
Objekt	O
(	O
object-oriented	B-Language
memory	B-General_Concept
management	I-General_Concept
unit	I-General_Concept
)	O
and	O
Klock	O
(	O
processor	O
clock	O
and	O
support	O
logic	O
)	O
.	O
</s>
<s>
Linn	O
intended	O
to	O
sell	O
the	O
Rekursiv	B-General_Concept
chip	O
set	O
to	O
vendors	O
,	O
as	O
well	O
as	O
produce	O
their	O
own	O
workstation	B-Device
using	O
it	O
.	O
</s>
<s>
Initially	O
,	O
the	O
only	O
product	O
was	O
"	O
HADES	O
"	O
,	O
the	O
"	O
Hardware	O
Accelerator	O
for	O
Dynamic	O
Expert	O
Systems	O
"	O
,	O
which	O
consisted	O
of	O
a	O
VMEbus	B-Architecture
card	O
that	O
could	O
be	O
plugged	O
into	O
a	O
Sun-3	B-Device
or	O
Sun-4	B-Device
workstation	B-Device
.	O
</s>
