safe_pause_us() is always at least 1 millisecond long

[Ryan Stone]

Using min is definitely not correct.  That would ensure that you
either got a pause of 1 tick or 0 ticks.

This may get you better granularity, depending on the system.

pause_sbt("e1000_delay", x * SBT_1US, x < 1000 ? 100 * SBT_1US : SBT_1MS, 0);