Pure Standard Cell Designs

In the following sections of this chapter, we studied the 2.5-D placement problem under the above mentioned three formulations pure standard cell designs with inter-chip contacts consuming substrate area, pure standard cell designs with inter-chip contacts on top of die surface, and mixed standard cell and macro designs corresponding to a flattened design style. 

In this section, we consider the second scenario of 2.5-D placement, where a hierarchical design style is applied and the inter-chip contacts can be placed above the top-level metal layer. 

Bipartition Based Placement Input netlist N Output cell location cellLoc[] 

Variables Q = FIFO queue storing the subnetlists to be partitioned Subroutines  

Center(Ni) //return the center location of the layout area that contains subnetlist Ni Begin 

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The objective of the 2.5-D placement problem is to map a cell netlist (pure standard cell or mixed macro/standard cell) to unique positions in a layered space as illustrated in Fig. 6.1. The inter-chip contacts are assumed to be placed on top of the chip with no need to consume substrate area. We need to differentiate two scenarios hierarchical and flattened design styles. In a hierarchical design set up, after the floorplanning step, cells in a block need to be placed. As mentioned in the last chapter, a random-logic based block could be split into two chips. The 2.5-D placement problem is to assign the cells within such a block to unique positions on two chips. On the other hand, in a flattened design style, the 2.5-D placement problem is to place both standard cell macros onto stacked chips. 

The original placement framework of Capo only supports pure standard cell layout. However, today typical VLSI designs contain certain number of macros, such as embedded memory and IP blocks. In a flattened design flow, placement engine has to be able to place macros and standard cells simultaneously. Accordingly, we enhance Capo with the capability to handle mixed macro/standard cell layout. 

One design of electrode is illustrated in Fig. 3.4. Pure mercury covers a platinum wire sealed through the bottom of a glass tube. The mercury is covered with powdered mercurous chloride, which is only slightly soluble in potassium chloride solution, the latter filling the cell. The activity of Hgi depends on the concentration of KCl since the solubility product (Hg2" )(Cl is a constant. Potentials on the standard hydrogen scale for various KCl concentrations are listed in Table 3.4. 

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