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Questions tagged [alu]

For questions related to Arithmetic Logic Units

5
votes
1answer
242 views

Were there any working computers using residue number systems?

Wikipedia says: A residue numeral system (RNS) is a numeral system representing integers by their values modulo several pairwise coprime integers called the moduli. Bit widths of each of those "...
8
votes
5answers
3k views

What was the main purpose of bitshift instructions in CPU?

As far as I know, even simple RISC microcontroller have a bitshift operator, and honestly I had to use it only once when I had to compute a division on a MCU that could not do divisions in the ALU. ...
7
votes
4answers
455 views

Which CPUs had instructions leaving data registers in an unspecified state?

When an ALU performs a floating point division operation using the non-restoring or the SRT algorithm, it maintains the current value of the "remainder" (in quotes, because it is not a true non-...
26
votes
4answers
9k views

How did 8 bit processors perform 16 bit arithmetic?

How did 8 bit processors such as the Z80 and 8080 perform 16 bit arithmetic? They have an 8 bit data bus, so how does the ALU perform 16 bit arithmetic on the register pairs? Z80 architecture diagram ...