Bits discarded in Multiplication 
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 Bits discarded in Multiplication

Hello,
Can anyone please tell me is multiplication unit a part of ALU or not?

If I've an ALU that takes two inputs say a and b each of 4-bits and an
output. To accomplish multiplication should output register of 4-bits
or 8-bits? If it is of 8-bits then in case of when the output of ALU
comes back again for another computation, how can it map 8-bit output
register to 4-bit input register? If it is of 4-bits, then in case of
multiplication the four bits of output would be discarded to fit in
4-bit output register.

Please guide me.
Regards
Atif



Wed, 16 Nov 2005 18:04:08 GMT  
 Bits discarded in Multiplication


Quote:
> Hello,
> Can anyone please tell me is multiplication unit a part of ALU or not?

> If I've an ALU that takes two inputs say a and b each of 4-bits and an
> output. To accomplish multiplication should output register of 4-bits
> or 8-bits? If it is of 8-bits then in case of when the output of ALU
> comes back again for another computation, how can it map 8-bit output
> register to 4-bit input register? If it is of 4-bits, then in case of
> multiplication the four bits of output would be discarded to fit in
> 4-bit output register.

> Please guide me.
> Regards
> Atif

Both ways are acceptable depending on the needs. In some architectures
the output is truncated so overflow is possible if care is not taken
on the inputs. In others, the output is split and stored into two
registers. Still in other architectures, the output register is special
and larger than normal to perhaps accumlate larger intermediate values
and at the end is trucated or split into smaller pieces.


Thu, 17 Nov 2005 04:30:39 GMT  
 
 [ 2 post ] 

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