This study examined the high-speed characteristics of a system in a package (SiP) including a system on a chip (SoC) and a double-data-rate-three synchronous dynamic random access memory (DDR3 SDRAM) chip. The SiP was a multi-chip-module thin-profile fine-pitch ball grid array (MCM TFBGA) package with a four-layer substrate. High-speed DDR3 signals with a 1600-Mbps data rate were used in the signal integrity (SI) analysis. The SiP with low-cost silver (Ag) wires displayed a 500.18-ps aperture width in an eye diagram, which successfully met the SI performance requirement. This study thus demonstrated that the SiP with Ag wires would have significant potential for advanced high-speed product applications.