In CPUs with flag registers, an earlier instruction sets a condition in the flag register. The earlier instruction may be arithmetic, or a logic instruction. It is often close to the branch, though not necessarily the instruction "immediately" before the branch. The stored condition is then used in a branch such as "jump if overflow-flag set". This temporary information is often stored in a flag register but may also be located elsewhere. A flag register design is simple in slower, simple computers. In fast computers a flag register can place a bottleneck on speed, because instructions that could otherwise operate in parallel (in several execution units) need to set the flag bits in a particular sequence.