What causes failure to boot into Mac OS 9?

[princealfie]

In 2003, Apple disabled the computers from being able to boot directly into Mac OS 9. What is the exact mechanism causing this?

Is there a workaround? Is this a software or hardware issue?

 

[mad jew]

It's a firmware issue in most of the Macs immediately preceding this, but a hardware issue in newer Macs. Sorry, I don't know a workaround though.

 

[nazmac21]

In 2003, Apple disabled the computers from being able to boot directly into Mac OS 9. What is the exact mechanism causing this?

Is there a workaround? Is this a software or hardware issue?

I think it's a firmware thing that Apple did. From that moment on, macs do not boot into OS 9 directly.

 

[synth3tik]

It is firmware, I do know that machines with FW800 can not run OS 9. beyond that I am not really sure.

 

[Sun Baked]

Not a firmware issues, more like a ROM issue (even though the ROM is on the HD.)

Remember the classic OS required OS, system file/utility changes, and ROM changes every time the hardware changed.

Once Apple froze the OS, any meaningful hardware change broke the OS.

Which is why the FW800 (and the USB move to the PCI bus) broke the OS 9 booting on PowerMacs, and why DDR RAM and the changes in the replacement Integrated North/South chip broke it in everything else -- the harware changed.

OS 9 could have booted on machines after this if people had written ROM patches (and openfirmware enablers) -- but the talent that used to get the old OS's booting on old machines had basically moved on.

The FW800 PowerMac would have likely been easy for them, the DDR Intrepid machines would have been rather difficult.