Changed HP15C firmware for Go15c?

[johanw]

SwissMicros patched the original HP15C rom image to allow more memory because the improved hardware allowed it. Which made me wonder: is it possible to extract the changed ROM image from the DM15 firmware? I would like to test if this changed firmware would make it possible to use the extra memory also on emulators like Go15, who use a rom file to function.

When I quickly compare both files I could not see where the 15C rom is located in the firmware, a search for the first few rom bytes in the unmodified firmware does show no match (I assume the firmware contains more than just the rom image).

Edit: I seem to have accidentily misposted this, it should go to the Not quite HP Calculators - but related section but I can't move the thread.

[grsbanks]

The (patched) ROM is encrypted in the SwissMicros firmware.

[johanw]

(09-16-2020 06:38 AM)grsbanks Wrote:  The (patched) ROM is encrypted in the SwissMicros firmware.

Grmpf. :-(

Well, that encryption can't be too good, all models use the same firmware file and the DM1x hardware has no provisions for secure key storage like modern Apple or Qualcomm socs. Maybe someone cracks it someday.