While backwards compatibility was maintained, the older access methods suffered from performance problems due to the address translation required for virtual storage.

Optional MMU supporting both memory protection and dynamic address translation.

The initial versions of the system provided no support for virtual memory and address translation.

Logical to physical address translation was carried out using a set of address translation tables.

Thus apertures form a layer of address translation below the level of the usual virtual-to-physical mapping.

Such address translations are carried out by the segmentation unit of the CPU.

For one, only two address translations are needed.

Doing so required hardware and microcode customization on a S/360-40, to provide the necessary address translation and other virtualization features.

The hint technique works best when used in the context of address translation, as explained below.

For the purposes of the present discussion, there are three important features of address translation: