The intent of this solicitation is to request proposals from organizations willing to serve as Resource Providers within the NSF eXtreme Digital (XD) program. The current solicitation is intended to complement previous NSF investments in advanced computational infrastructure by exploring new and creative approaches to delivering innovative computational resources to an increasingly diverse community and portfolio of scientific research and education. NSF's vision for Advanced Computing Infrastructure, which supports Cyberinfrastructure Framework for 21st Century Science and Engineering (CIF21), focuses specifically on ensuring that the science and engineering community has ready access to the advanced computational and data-driven capabilities required to tackle the most complex problems and issues facing today's scientific and educational communities. To accomplish these goals requires advanced computational capabilities within the context of a multilevel comprehensive and innovative infrastructure that benefits all fields of science and engineering. Previous solicitations have concentrated on enabling petascale capability through the deployment and support of a world-class High Performance Computing (HPC) environment. In the past decade NSF has provided the open science and engineering community with a number of state-of-the art HPC assets ranging from loosely coupled clusters to large-scale instruments with many thousands of computing cores communicating via fast interconnects, and more recently with diverse heterogeneous architectures. Recent developments in computational science have begun to focus on complex, dynamic and diverse workflows, which integrate computation into all areas of the scientific process. Some of these involve applications that are extremely data intensive and may not be dominated by floating point operation speed. While a number of the earlier acquisitions have addressed a subset of these issues, the previous solicitation NSF 13-528 and the current solicitation emphasize these aspects even further. Currently NSF operates, through Blue Waters and the eXtreme Digital (XD) program, a two-tiered comprehensive distributed Cyberinfrastructure (CI), which is one of the largest and most powerful in the world. Through these and related projects the open science and engineering community is currently capable of tackling many of the most challenging scientific problems across multiple science and engineering domains. Both of these tiers are explicitly designed to address needs beyond the campus level. With this solicitation, NSF intends to continue this model to broaden the CI capabilities above the campus level, while promoting deeper campus engagement. The resources supported under this solicitation will be incorporated into and allocated as part of the XD tier of national shared resources. The Extreme Science and Engineering Discovery Environment (XSEDE) integrates resources from the XD tier and will provide shared services for this resource in the form of: allocations, user support, training education and outreach services, an XSEDE-wide file system, which connects all the resources, and campus bridging. Additional XD shared services provided include the following: the Technical Inspection Service (TIS), dedicated to the evaluation of software and providing recommendations to XSEDE on the use of that software and the Technical Audit Service (TAS), dedicated to providing metrics for the systems supported within XD and also to the evaluation of applications on the XD systems. The TAS operates XDMoD, a publically available and easily usable tool to extract a broad array of information concerning the way the XD resources are providing services to the open science community. The current solicitation is intended to complement previous NSF investments in advanced computational infrastructure by exploring new and creative approaches to delivering computational resources to the scientific community. Consistent with the Advanced Computing Infrastructure: Vision and Strategic Plan ( February 2012), the current solicitation is focused on expanding the use of high-end resources to a much larger and more diverse community. To quote from that strategic plan, the goal is to "... position and support the entire spectrum of NSF-funded communities ... and to promote a more comprehensive and balanced portfolio .... to support multidisciplinary computational and data-enabled science and engineering that in turn supports the entire scientific, engineering and educational community." Thus, while continuing to provide essential and needed resources to the more traditional users of HPC, this solicitation expands the horizon to include research communities that are not users of traditional HPC systems, but who would benefit from advanced computational capabilities at the national level. Building, testing, and deploying these resources within the collaborative ecosystem that encompasses national, regional and campus resources continues to remain a high priority for NSF and one of increasing importance to the science and engineering community. Resource Providers--those organizations willing to acquire, deploy and operate NSF supported resources in service to the science and engineering research and education community--play a key role in the provision and support of a national Cyberinfrasructure. With this solicitation, NSF requests proposals from organizations willing to serve as Resource Providers within the eXtreme Digital (XD) program. In the past NSF has acquired and deployed these systems to the S&E community using the shared services model of the XSEDE project as described above. In that model, the resources are allocated via a competitive process, defined by NSF and managed by the XSEDE Resource Allocations Committee (XRAC). Depending on the type of resources and the objectives defined by the proposers, that process may require some accommodation or modification as is discussed below.Competitive proposals must address one or more of the following:Complementing existing XD capabilities with new types of computational resources attuned to less traditional computational science communities;Incorporating innovative and reliable services within the HPC environment to deal with complex and dynamic workflows that contribute significantly to the advancement of science and are difficult to achieve within XD;Introducing new, flexible, and highly usable capabilities such as cloud computing into XD to meet national-scale requirements for new modes of computationally intensive scientific research;Introducing new capabilities and/or reaching new communities by establishing novel, highly usable connections to other non-XD parts of the national cyberinfrastructure. For example, these might include connections to other domain-specific centers housing software, sensors or instrument data thus enabling new advances in computational science;Exploring new effective modes of engagement with campus cyberinfrastructure;Expanding the range of computationally challenging science and engineering applications that can be tackled with current XD resources. Again ease of access and usability are critical; andProviding reliable approaches to scientific communities needing a flexible and user friendly environment. This can be achieved in a variety of ways and the proposal should explicitly provide details on how that would be achieved by their approach.An important aspect of the current solicitation is that hardware acquisition must provide a high degree of stability and usability by no later than January, 2016. Note, that proposals to add new and innovative features to currently deployed systems are eligible for consideration. In past solicitations benchmarks have played an important role. Two types of benchmarks were required: NSF-provided and proposer-selected benchmarks. For this solicitation, given the emphasis on nontraditional HPC as well as possible cloud-like solutions, and the potential breadth in targeted scientific impact, NSF has opted not to require a set of NSF-provided benchmarks. Nonetheless, we still require that each proposer provide a convincing demonstration, with hard data, that their system will perform as described in their proposal. Benchmarks certainly can address applications that are currently used by the NSF computational science community but must also provide compelling evidence of the expanded scientific diversity and new communities that will be reached from the innovative aspects of the proposed resource. Clearly the details of the submitted benchmark results will depend on the nature of the proposed resource and are likely to differ from one submission to the next.