Cruise speed...
For the Global 5000 and XRS the speeds are as follows...
Keep in mind that maximum TAS and Mach vary with altitude/temperature and the higher you go the lower the MMO will be.
VMO (SL - 8000') = 300 KIAS
VMO (8000' - 30,267') = 340 KIAS
MMO (30,267' - 35,000') = 0.89M
MMO (41,400') = 0.88M
MMO (47,000') = 0.858M
MMO (51,000') = 0.842M
Normal cruise speed is 0.85M and we use for long range cruise speed when heavy 0.82M.
If you really want to go fast and fly as close to the VMO/MMO you would fly the Global between 30,000' and 41,000'.