Architecture Implications of Pads as a Scarce Resource: Extended Results

Report
Authors:Zhang, Runjie, Department of Computer ScienceUniversity of Virginia Wang, Ke, Department of Computer ScienceUniversity of Virginia Meyer, Brett H., Department of Computer ScienceMcGill University Stan, Mircea R., Department of Computer ScienceUniversity of Virginia Skadron, Kevin, Department of Computer ScienceUniversity of Virginia
Abstract:

Due to non-ideal technology scaling, delivering a stable supply voltage is increasingly challenging. Furthermore, competition for limited chip interface resources (i.e., C4 pads) between power supply and I/O, and the loss of such resources to electromigration, means that constructing a power delivery network (PDN) that satisfies noise margins without compromising performance is and will remain a critical problem for architects and circuit designers alike. Simple guardbanding will no longer work, as the consequent performance penalty will grow with technology scaling. In this report, we develop a pre-RTL PDN model, VoltSpot, for the purpose of studying the performance and noise trade-offs among power supply and I/O pad allocation, the effectiveness of noise mitigation techniques, and the consequent implications of electromigrationinduced PDN pad failure. Our simulations demonstrate that, despite their integral role in the PDN, power/ground pads can be aggressively reduced (by conversion into I/O pads) to their electromigration limit with minimal performance impact from extra voltage noise – provided the system implements a suitable noise-mitigation strategy. The key observation is that even though reducing power/ground pads significantly increases the number of voltage emergencies, the average noise amplitude increase is small. Overall, we can triple I/O bandwidth while maintaining target lifetimes and incurring only 1.5% slowdown.

Rights:
All rights reserved (no additional license for public reuse)
Language:
English
Source Citation:

Zhang, Runjie, Ke Wang, Brett H. Meyer, Mircea R. Stan, and Kevin Skadron. "Architecture Implications of Pads as a Scarce Resource: Extended Results." University of Virginia Dept. of Computer Science Tech Report (2014).

Publisher:
University of Virginia, Department of Computer Science
Published Date:
2014