The decoders 60901/60902 have 27 speed levels inside, in opposite of the old 6090 decoders. It is not possibele to acess them directly, because the Motorola data has only 14 external speed steps. With a special sequence of speed commands, it is possible to acess all internal speed levels directly. To do that, two speed commands with its locomotive number must be send.
For testing I took two indentical locos with different decoders. I adjust both locos to 100 km/h at ISL (internal speed level) 10. To do that, I send first speed command 11 and then speed command 10 to the locomotives. The chart below shows the relation between the old and the new decoders with ISL and real speed:
|Command||ISL 6090||ISL 60901||km/h 6090||km/h 60901|
It looks that locos with 60901 are 5 km/h slower then locos with old 6090 at top speed. All locos has speed flucuationen up to 2-3 km/h at top speed, so one can neglect it. The biggest advantage of the half speed levels is at shunting speed. A fantastic slow motion is possible at speed level 0,5, but the loco needs two pickup shoes, otherwise it will stop at the first turnout. Above the speed level 4 the half speed levels make not nuch sense, because the delay will compensate the bigger speed difference between the solid speed levels. Above speed level 10 it is impossible to see a difference between a running locomotive at speed level 9,5 or 10. Only the sound of the motor is different, after changing a speed level.