Both of the MDDs in this house are of the generations (1GHz DP: SG240..., and 1.25GHz: YM343...) that were intended to be able to boot into OS 9. Although neither came with the original System Install discs (they were second-hand), when I was able to get the machine-specific discs I found that the System Folder of OS 9.2.2 contained:
- Classic v9.5.0 (Classic Compatibility ROM v1.0)
Classic Support v.2.2.1 (Classic Compatibility Environment v1.9)
Classic Support UI v.2.2.1 (Classic Compatibility Environment v1.9)
Mac OS ROM v10.2.1 (Mac OS CPU Software v5. 8) : this is the 'ROM in RAM'.
I don't know whether these all, or the ROM in RAM alone, determine the ability to boot into OS 9, or whether that can be defeated by hardware. It does give you a line for exploration, however, if your install disc is not suited to the MDD that you have. For example, Mac OS ROM v9.7.1 is on my 'retail' OS 9.2.1 CD, and definitely does not support 48-bit LBA for HDDs, whereas v10.2.1 does.
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