What SQM is trying to solve
When a connection is saturated, large queues can increase latency. Smart queue management uses controlled shaping and scheduling to keep queues shorter and make interactive traffic more responsive.
Why speed can decrease
Traffic shaping can lower measured peak throughput because the router deliberately controls the link. The goal is often better latency consistency rather than the highest possible speed-test number.
CPU capacity matters
High-speed connections can overwhelm older router CPUs when complex queue disciplines or VPN processing are active. Hardware acceleration interactions may also affect results.
Tune with repeatable tests
Change one setting at a time, record baseline latency and throughput, then test under both download and upload load. Revert changes that provide no measurable benefit.
Practical takeaway
Keep changes model-specific, document your current settings, and test one change at a time. That approach makes future upgrades and troubleshooting much easier.