A memory subsystem empirically tests performance parameters of I/O with a memory device. Based on the empirical testing, the memory subsystem can set the performance parameters specific to the system in which the memory subsystem is included. A test system performs the testing. For each of multiple different settings for multiple different I/O circuit parameters, the test system sets a value for each I/O circuit parameter, generates test traffic to stress test the memory device with the parameter value(s), and measures an operating margin for the I/O performance characteristic. The test system further executes a search function to determine values for each I/O circuit parameter at which the operating margin meets a minimum threshold and performance of at least one of the I/O circuit parameters is increased. The memory subsystem sets runtime values for the I/O circuit parameters based on the search function.