Abstract: A computer system for executing branch instructions and a method of executing branch instructions are described. Two instruction fetchers respectively fetch a sequence of instructions from memory for execution and a sequence of instructions commencing from a target location identified by a set branch instruction in a sequence of instructions being executed. When an effect branch signal is generated, the target instructions are next executed, and the fetcher which was fetching the instructions for execution commences fetching of the target instructions. The effect branch signal is generated separately from the set branch instruction. In another aspect, the effect branch signal is generated on execution of a conditional effect branch instruction, located at the point in the instruction sequence where the branch is to be taken.

Abstract: A computer system for executing branch instructions and a method of executing branch instructions are described. Two instruction fetchers respectively fetch a sequence of instructions from memory for execution and a sequence of instructions commencing from a target location identified by a set branch instruction in a sequence of instructions being executed. When an effect branch signal is generated, the target instructions are next executed, and the fetcher which was fetching the instructions for execution commences fetching of the target instructions.

Abstract: A computer system for executing branch instructions and a method of executing branch instructions are described. Tow instruction fetchers respectively fetch a sequence of instructions from memory for execution and a sequence of instructions commencing from a target location identified by a set branch instruction in a sequence of instructions being executed. When an effect branch signal is generated, the target instructions are next executed, and the fetcher which was fetching the instructions for execution commences fetching of the target instructions. The effect branch signal is generated separately from the set branch instruction. In another aspect, the effect branch signal is generated on execution of a conditional effect branch instruction, located at the point in the instruction sequence where the branch is to be taken.

Abstract: There is disclosed a computer and a method of operating a computer to allow combination of data values in the context of the execution of so-called "packed instructions". A data string comprising a certain number of sub-strings representing discrete data values and which are not independently addressable is held in a source register store. A combining instruction which operates to carry out a polyadic operation on at least some of the sub-strings to generate a result sub-string is then executed.A result data string comprising said result sub-string is loaded into a destination register. These "combining" instructions have the advantage that they are general purpose instructions which can be used in a plurality of different situations. The instructions are particularly useful in a packed arithmetic environment.

Abstract: There is disclosed an arithmetic unit which allows a combined multiply-add operation to be carried out in response to execution of a single computer instruction. This is particularly useful in a packed arithmetic environment, when a operand comprises a plurality of packed objects and the intention is to carry out the same arithmetic operation on respective pairs of objects in different operands. There is also provided a computer and a method of operating a computer to effect the combined multiply-add operation.