So from what you said Diehard then at the open firmware level everything is opened up at startup - then it's at the startup of the Mac Operating System that depends whether the ports are used or not?
No, I am NOT saying that... Let's NOT confuse Open firmware with SMC Firmware UpdatesApple's Open Firmware is part of their ROM-in-RAM design approach originally used in the first iMac systems. The approach uses a small ROM that contains sufficient code to initialize the hardware and load an operating system. The rest of the system code, that on previous Mac systems (old world) resided on a physical ROM (chip) is now loaded from disk or from network into RAM. Open Firmware is part of this "New World" boot system.
So as my understanding is... open firmware is at a higher level than the actual SMC firmware... and thus you can use Open firmware commands to re-burn read only hardware updates into SMC firmware and NOT effect the Open Firmware itself.
Any experts that can better explain the relationship between the SMC / Firmware and OS ROM... please "chime" in...
Startup Sequence... As explained by apple... in the simplest way... 1. Turn on the computer.
2. Hardware self-test.
3. Mac OS starts up.
4. Search for a startup disk.
5. System file is found and opens.
6. System extensions load.
7. Finder opens.
8. Startup Items open.
#2 & #3 are obviously more involved, and where most of our discussion comes from. We have all heard of "Resetting the SMC" on a G4.
The SMC (System Management Controller) controls a number of the Mac's core functions. The SMC is a chunk of hardware incorporated into the Mac's motherboard. Its purpose is to free the Mac's processor from having to actively take care of rudimentary hardware functions.
So basically this "Chunk of Hardware" is obviously a chip or series of chips that are physically located on the MB, and some values that these chips hold can be cleared (By hitting the SMC" reset button and giving a small voltage zap) and thus new "correct" values will be re-read and re-written into the SMC upon power on and the SMC will see everything peachy and BAM... a familiar C Chord Chime will be heard.
Depending on your Mac model, the SMC performs the following functions:
Responds to the press of the power button, including deciding whether the press is for a power off, sleep
Detects and responds to the opening or closing of the lid of a portable Mac.
Manages a portable's battery performance, including charging, calibration, and displaying remaining battery time.
Thermal management of your Mac's interior. This is primarily accomplished by sensing temperature at various places inside your Mac, and then adjusting fan speed to create or reduce airflow.
And... a whole bunch of other stuff
Step 2: Hardware Self-Test
After the computer is turned on, different "managers" in the computer's read-only memory begin to function. The first is the Start Manager. It makes sure that certain hardware components on the computer's logic board are working, including the microprocessor, read-only memory, drives, ports, expansion slots, and memory (RAM).
The startup sound you hear when you turn on the computer indicates that the Start Manager has successfully completed its tests. You will also see the raster (gray desktop) on the screen, along with the pointer.
If one of the Start Manager tests fails, you may hear a series of tones (sometimes called "error tones" or "death chimes") see a "sad Macintosh" icon on the screen The kind of tones you hear will vary depending on the Macintosh model, and on the kind of component(s) that failed the test.
So when we talk about updating firmware... I believe we are talking about updating SMC firmware or more exactly updating the read only executable code that communicates directly with the SMC chips (or series of chips). In our experiment the system management controller hardware on the MDD FW400 and MDD FW800 are obviously close enough that the Startup manager sees all values from the SMC as cool and chimes (if not, Blitter would have gotten error beeps and no Chime after the force burn)... and thus a "dead" MDD.
Since the SMC communicates directly with the hardware on the MB at a very basic level... I am guessing it is seeing the FW800 ports as FW400 Ports upon boot sequence (and does NOT look for 800 ports, since a FW400 MDD does not have any)... after boot sequence in OS X... I can only guess that OS X drivers get some values from the SMC (temperature and other stuff) but access the FW ports directly and ignore where the SMC says they are... where as OS 9 may rely more on what the SMC says and not look for something the SMC does not see.
- Diehard
PS: I could be 100% wrong with this post...hehehe
