HotSpot-3.0.1 Changes
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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.
