This outputs a value based on whether the system is running using New 3DS CPU speed and whether the application is registered with APT (see APT:Enable).
Using New 3DS CPU speed (i.e. modes 2 and 4) seems to be known as running as an "ext application" (probably for "extended application").
Application Running Mode
| Value
|
Description
|
| 0
|
No application is running
|
| 1
|
Old 3DS CPU speed, registered with APT
|
| 2
|
New 3DS CPU speed, registered with APT
|
| 3
|
Old 3DS CPU speed, not registered with APT
|
| 4
|
New 3DS CPU speed, not registered with APT
|