Specific form factor requirements of the mobile thin and light platform limit the kinds of cooling solutions these platforms can have. As a result, individual components inside mobile platforms (such as system memory devices) can heat up. With increased memory speeds and capacities, we are now reaching the point where the memory thermals are starting to exceed the cooling capabilities of mobile systems. To ensure that the memory devices operate within their thermal limits, their case temperatures need to be monitored and memory accesses throttled if any memory device overheats. In this paper, we discuss the need for memory throttling and address two memory throttling techniques, implemented in platforms built on Intel® Centrino® Duo mobile technology. These techniques greatly improve the memory power/thermal management in a thermally constrained platform by maximizing performance while keeping the system within its thermal limits.

First, we describe Delta Temperature (DT) in Serial Presence Detect (SPD), a novel memory throttling technique, which uses the Virtual Temperature Sensor (VTS) throttling mechanism (VTS was first implemented in the Intel® 815GMCH chipset) to optimize memory throttling control. VTS provides the means to predict the temperature of the memory devices in platforms that don’t have a physical thermal sensor on the DRAM modules. When the predicted temperature exceeds the set memory thermal limit, throttling is enforced. We also discuss the implementation details of DT in SPD and the performance benefits it offers in terms of guardband reduction and bandwidth recovery, over the existing open loop throttling techniques.

Finally, we focus on Thermal Sensor (TS) on a Dual In-line Memory Module (DIMM), a closed loop solution for memory throttling control. This technique uses a physical thermal sensor on each of the memory modules that signals the chipset to throttle memory traffic when the memory module exceeds the thermal trip-point. Adding a thermal sensor to the memory module allows the system to continue running at full bandwidth until the critical temperature is reached. In addition to providing both a mechanism for preventing the DRAMs from exceeding the maximum temperature specification (85°C for memory) and a mechanism to control skin temperature, we discuss the performance benefits that TS on DIMM offers over existing VTS-based solutions, including guardband reduction and bandwidth recovery.