Hello & welcome, Werner !
ok did some more tests - the ixus980 seems to ignore different diskboot.bin files from other cameras - using the diskboot.bin from ixus980 version 1.00e the camera crashes as expected.
The firmware update loading mechanism always checks whether the Platform-ID
is the correct one for this camera model.
Different firmware versions (and also different "brands" like Powershot/IXUS/IXY or PAL/NTSC cameras) have the same P-ID.
A "foreign" CHDK (i.e. with the wrong P-ID) will be rejected with an error message or will be ignored...
So, since the 1.01B fw is not yet supported, it must be ported first...