Slow memory refresh in a computer with a limited supply of power

摘要

A power suspend mode activates a slow DRAM refresh in a computer system with a limited source of power. The power suspend mode reduces the power consumed by the computer system while preserving the contents of memory. The cyclic refresh of DRAM using a slow refresh clock substantially reduces the power consumed while the computer is suspended. This technique is particularly useful for battery powered portable computer systems. When an external or internal condition causes the computer system to transition to a power down mode, an IO subsystem notifies the CPU which sets control bits in the IO subsystem and a video subsystem. The IO subsystem then begins to generate a slow DRAM refresh pulse. Once the CPU and video subsystem sense the power suspend mode activation, the system memory and video memory are refreshed using the slow refresh clock. The power consumed during the refresh process is thereby greatly reduced. When a resume signal is received by the IO subsystem, the slow refresh clock is terminated and the system memory and video memory are again refreshed using a normal faster clock.