Elliott 4130

The 4100 series machines were based on bit-parallel CPUs employing silicon transistors. For each of the 4120 and 4130 computers there was originally a choice of ferrite core store: either 2 microsecond or 6 microsecond cycle time. The 4130 had a faster CPU and implemented floating-point operations in hardware. Floating-point was performed by software extracodes in the 4120. The Autonomous Transfer Unit (ATU) was an add-on extra for the 4120 but was built into the main cabinet of a 4130. Importantly, the 4130 incorporated multiprogramming hardware. It could operate in two modes, executive mode and user mode. It could run multiple 'slaves', which were contiguous areas of memory (not swappable) allocated to different applications. Typically, one could run batch programs and another might be a special one for operating a slow peripheral such as a plotter.