IXUS 265 HS, firmware 1.00b — CHDK working (unofficial patched build attached)
In the interest of transparency: I'm not a CHDK developer. I worked this out with the help of an AI assistant (Claude), which did the firmware comparison and the patch. I did all the testing on my own camera and checked the results.
Findings: the 1.00b and 1.00c dumps (both linked from the wiki) differ by only 11 words in the main firmware image: the build date, the version string, two constants and two table values. None of them is at an address the 1.00c port uses. Same P-ID (0x3289), and the version string is at the same address (0xff0a4c59).
What was changed: I took the official 1.00c test build (1.6.0-5821), decoded DISKBOOT.BIN with tools/dancingbits (key 12), changed the loader's expected version string from GM1.00C to GM1.00B and re-encoded it. Re-encoding the unmodified file reproduced the original exactly. The only difference from the original DISKBOOT.BIN is encoded byte 729 (0xbc → 0xbd).
Patched DISKBOOT.BIN MD5: f7e1c205150c394a227223ec1a7b05db
PS.FI2 removed (it can't be patched without the keys), so it's bootable-card only
Everything else is unchanged from the 1.00c test build
Tested on 1.00b (32 GB FAT32 card, BOOTDISK at 0x1E0, card locked):
Boots with the CHDK splash
ALT mode on Play and the CHDK menu work
RAW/DNG saves and opens correctly on macOS
Tv override with Long Exp. 5 s works: the shutter stays open and the EXIF shows 5 s
Suggestion: add ixus265_elph340hs,100b,ALPHA,100c, to camera_list.csv (the same approach as ixus255 100h), so 1.00b gets a proper build and the attached file isn't needed. Happy to test further builds.
