I
174ijO Floating point reciprocal approximations of
(Vj
elements) to
Vi
elements
This
instruction
is
executed in the reciprocal approximation unit.
The
instruction
forms
an
approximate value of the reciprocal of the
normalized floating point quantity in
each
element of
Vj
and
enters
the
result
into elements of
Vi.
The
number
of elements for
which
approximations are
found
is
determined
by
the contents of the
VL
regi
ster.
The
174
instruction
occurs in the divide sequence to
compute
the
quotients of floating point
quantities
as
described in Section 3
under Floating Point Arithmetic.
The
reciprocal approximation instruction produces
results
that
are
accurate to
30
bits.
A
second
approximation
may
be
generated to
extend the accuracy to
47
bits
using the reciprocal
iteration
instruction.
Hold
issue conditions
034
-
037
in process
Exchange
in process
Vi
or
Vj
reserved
174
in process, unit
busy
for
(VL)
+ 4
CPs
Execution
time
Instruction issue 1
CP
Vi
ready
21
CPs
if
(VL)~
5
Vi
ready
(VL)
+
16
CPs
if
(VL)
>
~
<oJ
Vj
ready
5
CPs
if
(VL)
~
5
Vj
ready
(VL)
CPs
if
(VL)
> 5
Unit ready
(VL)
+ 4
CPs
Chain
slot
ready
16
CPs
2240004
4-68
£-01
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