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SkyCapt's picture
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Joined: 2017 Jan 11
NewWorld PPC, how do I get chksum from & dump backup MLB BootRom

PowerMac G4 MDD, my bootrom is functioning but I do not trust that it is the same ROM which would be installed if I were to run the official "Firmware" update/restore program, which I have never run.

Is there an official chksum, way to obtain chksum, and list of expected chksum? Can I dump my rom to a file for backup?

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SkyCapt's picture
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Joined: 2017 Jan 11

Checksum of BootRom is one of the 'steps' taken in "Apple Hardware Test". Step utilizes PPC code in the AHT file named "TCMs/TCMROM" (AHT v1xx) or "TCMs/of_rom.tcm" (AHT v2xx). TCM means something like Test Case Module, TCMs are in the format of Mac OS Shared Library.

I think passing (no error encountered) AHT's ROM Checksum step does not mean I possess the same ROM as you, but just means my ROM is not corrupted unto itself. I need to document my ROM's checksum, and, even matching checksums aren't necessarily identical ROMs, if anyone wanted to make changes to a ROM but hide those changes they can by manipulating some unused ROM bytes such that the desired checksum is what gets reported. That's possible, right? So I really want a chksum & DUMP of my MDD's ROM.

The ROM TCM library is only a few thousand bytes small, easily disassembled. Somebody should make a utility program that can report the checksum and make the dump. Wish I could, but, anybody?