L11:Computer Architecture

8-2 Two-Bus Organization
Using two buses is a faster solution than the one-bus organization. In this
case, general-purpose registers are connected to both buses. Data can be
transferred from two different registers to the input point of the ALU at the
same time. Therefore, a two operand operation can fetch both operands in the same
clock cycle. An additional buffer register may be needed to hold the output of the
ALU when the two buses are busy carrying the two operands. Figure (8.2)(a) shows
a two-bus organization.
In some cases, one of the buses may be dedicated for moving data into
registers (in-bus), while the other is dedicated for transferring data out of the
registers (out-bus). In this case, the additional buffer register may be used, as one of
the ALU inputs, to hold one of the operands. The ALU output can be connected
directly to the in-bus, which will transfer the result into one of the registers. (8.2)(b)
shows a two-bus organization with in-bus and out-bus.
8-2 Two-Bus Organization
Using two buses is a faster solution than the one-bus organization. In this
case, general-purpose registers are connected to both buses. Data can be
transferred from two different registers to the input point of the ALU at the
same time. Therefore, a two operand operation can fetch both operands in the same
clock cycle. An additional buffer register may be needed to hold the output of the
ALU when the two buses are busy carrying the two operands. Figure (8.2)(a) shows
a two-bus organization.
In some cases, one of the buses may be dedicated for moving data into
registers (in-bus), while the other is dedicated for transferring data out of the
registers (out-bus). In this case, the additional buffer register may be used, as one of
the ALU inputs, to hold one of the operands. The ALU output can be connected
directly to the in-bus, which will transfer the result into one of the registers. (8.2)(b)
shows a two-bus organization with in-bus and out-bus.