LCU

Unfortunately, the number of rods in the LCU is quadratic in the width of the ALU, so a reasonable width has to be chosen.

Babbage-Boole Digital Arithmetical and Logical Mill: Part 1 « The Half-Baked Maker 2009

The delay of the LCU is a problem, because the output of the LCU is required for the M1 equation, and the inputs to the LCU requires the A’ and B’ equations.

Babbage-Boole Digital Arithmetical and Logical Mill: Part 1 « The Half-Baked Maker 2009

The navigation systems have a unique feature called LCU (Lost?

Moneycontrol Top Headlines 2009

Instead, we could split the LCU into three boxes, one on top of the other.

Babbage-Boole Digital Arithmetical and Logical Mill: Part 2 « The Half-Baked Maker 2009

This means that M1 has to be delayed by 3 to allow enough time for the LCU to generate its output, meaning that the entire ALU now has a delay of 9 instead of 6.

Babbage-Boole Digital Arithmetical and Logical Mill: Part 1 « The Half-Baked Maker 2009

So the total delay for the lookahead carry unit (the LCU) is 3.

Babbage-Boole Digital Arithmetical and Logical Mill: Part 1 « The Half-Baked Maker 2009

Using a lookahead carry unit (LCU) is not inauthentic.

Babbage-Boole Digital Arithmetical and Logical Mill: Part 1 « The Half-Baked Maker 2009

The LCU will use the standard generate/propagate equations:

Babbage-Boole Digital Arithmetical and Logical Mill: Part 1 « The Half-Baked Maker 2009

Because of the bit slice architecture, the number of rods (with the exception of the LCU) is linear in the width of the ALU.

Babbage-Boole Digital Arithmetical and Logical Mill: Part 1 « The Half-Baked Maker 2009

This way, the LCU boxes are stacked on top of each other, and the maximum width is 24 instead of 44, which compares favorably with the 27 width of the X boxes.

Babbage-Boole Digital Arithmetical and Logical Mill: Part 2 « The Half-Baked Maker 2009