DRAM latency remains a critical bottleneck in the performance of modern computing systems. However, the latency is excessively conservative due to the timing margins imposed by DRAM vendors to accommodate rare worst-case scenarios, such as weak cells and high temperatures. In this study, we introduce a temperature- and process-variation-aware timing detection and adaptation DRAM (TPDA-DRAM) architecture that dynamically mitigates timing margins at runtime. TPDA-DRAM leverages innovativein-situcross-coupled detectors to monitor voltage differences between bitline pairs inside DRAM arrays, ensuring precise detection of timing margins. Additionally, the proposed detector inherently accelerates the precharge operation of DRAM, thereby reducing the precharge latency by up to 62.5%. Building upon this architecture, we propose two variation-aware timing adaptation schemes: 1) a process-variation-aware adaptation (PVA) scheme that accelerates access to weak cells, mitigating process-induced timing margins, and 2) a temperature-variation-aware adaptation (TVA) scheme that leverages temperature information and the restoration truncation technique to reduce DRAM latency, mitigating temperature-induced timing margins. Evaluations on an eight-core computing system show that TPDA-DRAM improves average performance by 21.8% and energy efficiency by 18.2%.