ixus990_sd970 porting thread:
https://chdk.setepontos.com/index.php?topic=13966.0

Camera specifics:
- Has an ND filter
- Does not have an iris
- propset 2
- ALT button is PRINT
- Supports multi-partition for cards larger than 4GB, does not support booting
  from singe partition FAT32


What's known to be missing:

- while zebra works edge overlay is stretched for 1px to cover 2px 
   (only upper half image used on full screen)
- whatever video stuff needs to be done beyond what sd780 implemented
- stubs_min.S "recreview_hold" is not set
- testing of FW 100B (should work but is untested)
   - If you can test that report here: https://chdk.setepontos.com/index.php?topic=13966.0


What koshy thought to be done:

- boot & spytask
- powerup sequence by Play and Rec buttons
- keyboard, all CHDKPTP buttons tested
- jogdial, including CHDKPTP buttons
   - jogdial no longer gets through to Canon FW
   - jogdial controls CHDK menus just fine
- shooting DNG
   - ColorMatrix / ForwardMatrix
   - ActiveArea
- USB remote is tested
- Quick press of shutter button does write DNG
- Custom palette for Rec mode including Func palette
- Long time exposures > 60 sec. tested working
- CHDKPTP File write task is tested
- CHDKPTP Palette is working
- CHDKPTP Liveview is implemented for all modes including Video 320
- the 25 tests reyalp and koshy used to run on a lot of cameras recently all pass
- Zebra is working
- implemented the same Movie related stuff as on sd780 but did not test it