It is now generally accepted that traditional backplane operation at 25 Gbps is possible if state-of-the-art design techniques are used. These techniques can include sophisticated equalization, multi-level modulation, forward error correction, and the use of premium dielectric materials and connectors. Signal integrity engineers are now considering whether link speeds beyond 25 Gbps are achievable using electrical architectures or whether a shift to optical solutions is required. This paper examines traditional and alternative copper backplane architectures to determine what speed, beyond 25 Gbps, is possible per differential link. Architectures that are studied include standard backplane links, shorter mid-plane orthogonal systems, and low-loss cabled solutions. All channels use existing components, and simulations employ advanced signal recovery techniques in order to push electrical signaling as fast as possible.