[The FireWire 800 G4 did away with booting into OS 9, although they kept the previous-generation G4 around as the "OS 9-bootable" model even after the FW800 G4 was replaced with the G5.

The September 2003 G4 iMacs (1 GHz 15", 1.25 GHz 17") cannot boot OS 9, the earlier models can, although I am not 100% sure about the February 2003 17"er.

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The cutoff point in the iLamp (LCD iMac with round base and chrome arm) was in the midst of the 800 MHz G4 17". So there is one 800 MHz G4 model with a 17" LCD which can boot into OS9, and another 800 MHz G4 model with a 17" LCD which does not boot into OS9.

As far as I can tell the only difference is the model number, although my memory is hazy, they may have different video chips. Everymac.com does a good job in this case of distinguishing the two models and giving model numbers.

It is interesting, because when I search Apple's documentation for the model number of the one which does boot into OS9, I can't get them to admit that it exists. Yet, using the information on everymac.com, I bought one for my son this past holiday season and made sure it had the "non-existent" model number.

So it definitely exists, whatever Apple may think.

Ah, went and double checked everymac.com. The OS9 bootable version uses an NVidia GeForce4 MX, while the later non-OS9 bootable has a Geforce2 MX, which seems a little backwards.

On closer examination, everymac.com states that the Feb, 2003 non-OS9-bootable is a 15". All this time I thought it was a 17". Hmmmm. I could swear there were 800 MHz 17" which are not OS9 bootable. Hmmm.