S-TDMA is a concept to realize coexistence of RT (real-time) and non-RT traffic over switched Ethernet by separating them in a time-slot basis. Theoretically, coexistence is achieved even in multi-hop network if precise time synchronization among the all nodes on its communication path. However, since it is technically difficult, the construction of wide-area S-TDMA network was not yet achieved. This paper implemented S-TDMA switch on NetFPGA-1G-CML board with 1 Gbps Ethernet PHY, newly adding a few nanoseconds-level time synchronization and change-mode mechanism to the previously presented implementation. Remarkably, this implementation enabled to examine the degree of throughput deterioration of non-RT with change-mode in one S-TDMA switch. Previous works regarding S-TDMA switch have never researched this issue. From the result of 1 ms period, TCP throughput was 14:65 Mbps when non-RT time-slot occupies 90% of each period. It was the worst value and only 4% of the result when non-RT time-slot occupies 100%. Such value is considered not practical if S-TDMA network is constructed in the real Internet infrastructure. Thus, further approaches to enhance TCP performance are discussed.