Powerbooks & System Enablers

[Paralel]

When it comes to Powerbooks and System Enablers, what exactly does the System Enabler do? If I put a Powerbook 550c processor into a 540c, would I need to run the 550c enabler since the ROM is from the 550c now or the 540c since that is what makes up the rest of the machine?

 

[NJRoadfan]

A system enabler contains resources for a specific system to run a particular version of MacOS that was designed prior to the hardware being released. Since it isn't documented anywhere(*), it likely contains the following:

-A memory map of the system being booted

-Drivers for any special hardware like audio, video, system chipset, etc.

*It surprises me that after all these years, nobody has disasembled and done a low-level analysis of the Classic MacOS system "kernel", ROM, and system enablers. To this day, articles about the OS say the boot process is shroulded in mystery and that pre-Open Firmware Macs can only boot MacOS before kick starting another OS.

 

[Elfen]

NJRoadfan has it right on the nose.

But the 550c and the 540c should be similar enough to work on the same OS (according to the technical notes I seen). But System enablers were for System 7 and in 7.6.1 should have ended their use as Apple promised then "No More System Enablers" in System 7.6+. But from System 7.6.1 to OS 8. Thus OS 8 can boot from some 030 macs, most 040 macs and all of the PowerPC Macs of the time without enablers.

@NJRoadfan - All, at least all 68K, Macs start with their ROMs at $00000000 and then there is some electronics Voodoo to bit-flip the ROM's addresses in hardware to just above $40000000 or $80000000 (depending on system) and start the system from there. There's no actual moving of the ROM other than shifting its hardware address registers, and then it opens up memory at $00000000 and clears and counts the RAM from there. That has been some serious Apple Voodoo secret for the longest, but we think we can figure out how its done in hardware. In software its easy, in hardware it gets tricky.

 

[Paralel]

Okay, then it sounds like the 540c enabler will still be the one that needs to be used. The memory map should be the same for both systems since they have the same ROM sizes and they both accept the same RAM modules and have the same maximum RAM amounts.

I'll also have to run TattleTech on both the 540c processor and the 550c processor to get the ROM versions and sub-versions to see if they match. The Apple technical specifications list the ROM ID and Ver for the 550c, but strangely they are not listed for the 520, 520c, 540, nor the 540c.

Finding a copy of the installation media for the 550c is proving to be extremely difficult. I have had no luck thus far, and apparently that installer is the only one that contains the Powerbook 550c Enabler

 

[Paralel]

I have definitive proof that a 550c processor will run on a 540c using the stock Powerbook 500 Series Enabler 1.02 that comes with any 540c.