HotSpot-3.0.1 Changes --------------------- 1. Release 3.0.1 fixes a few bugs in release 3.0. The most important of them being the way the dead space around the edge of the chip is modeled. In the previous release, the dead space was modeled as four thin strips around the chip with aspect ratios that were vastly different from the other blocks. This resulted in parasitic shorting of the lateral resistances of the blocks near the corner of the chip. This has been fixed now by splitting the rim strips into multiple blocks corresponding to the corner functional blocks. In cases when the floorplan consists of significantly different aspect ratios and granularity, the block model could result in some inaccuracy. An example for such a floorplan would be a fine-grained variation of the standard floorplan that comes with HotSpot, where the register file alone is sub-divided into a large number of (say 128) entries. In order to avoid such inaccuracies while using such a floorplan, use the 'flp_create_grid' function provided in 'flp.c' to create an equivalent floorplan that can be modeled accurately in HotSpot. The 'flp_create_grid' function creates a non-uniform, grid-like floorplan equivalent to the given floorplan, where there is no partial sharing of edges between blocks. This eliminates the inaccuracy that can arise due to the block model's way of computing the lateral resistances. 2. This release provides a choice to the user for the mapping between the grid and block temperatures of the grid model. Previously, the temperature of a block reported by the grid model was only the average of all the grid cells in it. Now, there are four options available. The 'min', 'max' and 'avg' options mean that the block's temperature is computed as the minimum, maximum, or average temperature of the grid cells in it. The 'center' option means that the block's temperature is given by the temperature of the grid cell at its center. 3. It is to be noted that for the same power density, the temperatures reported by the block and grid models could differ from each other. This is because both these models are fundamentally different in their organization. Closer match can be observed when the grid model's mapping mode is set to 'max' - i.e., the single temperature reported by the block model is closer to the maximum temperature within a block as computed by the grid model. We are currently working on making the two models more accurately consistent. Please look for updates soon at the HotSpot web page.
