That actually began as a research project when I asked him to verify the differences between the Portable ROMs and PB100s, mainly to validate Apple's claim that they were the same (which is not the case) and whether the Portable ROM had SCSI disk mode built in but not implemented.

Click to expand...

Wandering way off topic, but possibly helpful to Mac128...

Around about the time of the Portable launch, Apple and Outbound Systems settled their legal differences privately. Apple was provided access to Outbound's technology for portable Mac computers and Outbound were allowed to buy Mac ROMs directly. This information is all from the trade and legal press of that time. And the best Outbound technology was, arguably, SCSI Disk Target Mode.

Given that the Portable would have been close to completion when Apple and Outbound were agreeing terms, it is unlikely that any Outbound technology was incorporated in the Portable. I consider it unlikely that the Portable ROM was modified at such a late stage -- it would have required far too much regression testing. I'm happy to be contradicted by anyone capable of a disassembly. It is more likely that the Disk Mode feature was added to the PB100 ROM along with the other essential functionality changes: for an external floppy drive only, no PDS slot, different RAM timings, different power management for a different battery.

I guess that Apple's statement that the ROM in the Portable and PB100 is "identical" was not intended to be taken literally. For high level programs running on System 6 or System 7, the ROMs are the same. For low level programs (eg a RAM tester or battery rejuvenator), there are significant differences.