RCA 70/46 Reference Manual page 151

Multiply Word
(MR) (M)
General Description
Format
(RR)
(RX)
Condition Code
Interrupt Action
Fixed-Point
Instructions
• The operand (multiplicand) specified by the first address (Rd is
multiplied by the operand (multiplier) specified by the second address
(R 2 or
Xd B 2/D
2 ) .
The double-length p-roduct is loaded into the register
specified by the first address (R
1 ) ,
which must be an even number, and the
next odd-numbered register.
I
(MR)
10
Rl R2
0
7 8 11
12 15
I
(M)
50
Rl
X 2
B2
0
7 8 11
12 15 16 19 20 31
• Unchanged.
• Address error:
Addressing (RX format).
Specification.
Notes •
1. The first address (R
1 )
must always refer to the even-numbered regis-
ter of an even/odd pair. The multiplicand is taken from the
odd-numbered register of the pair. The original contents of the
even-numbered register, which is replaced by the product, is ignored.
An overflow cannot occur.
2. Only when two maximum negative numbers are multiplied does the
product exceed 62 significant bits. This product produces 63 signifi-
cant bits.
3. In two's-complement notation, the sign bit is propagated right, up
to the first significant product bit.
4. The sign of the product is determined algebraically. A zero result
is always positive.
5. The least significant digit of the product goes into the odd-numbered
register.
6. The operand specified by the second address (multiplier) is unaltered
except when the first and second addresses specify the same (even
numbered) register. In this case the multiplier is taken from the
even register, the multiplicand is taken from the odd
regis~r
and
the product is placed into the even/odd pair.
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