Here is a third beta test for Teensyduino 1.38.

Old beta download links removed. Please use the latest version:

Changes since Teensyduino 1.38-beta2:

Support for Arduino 1.8.4
fix for disable of SD on Teensy 3.5 & 3.6 (Frank)
SPI.transfer(readbuf, writebuf, size) (KurtE)
Added TeensyThreads library (Fernando Trias)
Fixed Adafruit_CC3000 on Teensy 3.x
Audio envelope graceful handling of noteone while gain > 0
Improved FreqMeasureMulti countToNanoseconds
[Experimental] EventResponder
[Experimental] MillisTimer
[Experimental] SPI async using DMA & EventResponder (KurtE)