I can confirm that the 867/1Ghz family motherboards are NOT compatible with the 1.33Ghz. I've used and replaced both of them (My mod for the GMMC this year was based upon both an 867Mhz G4 12 and a 1.5Ghz G4 12.) and the 1.5Ghz contain the support skeleton in which the motherboard mounts to (Or half at least), my 867Mhz did not, the motherboard screwed right into the case. The DC-Jacks are compatible, the DC to DC boards are not. Also, heatsink wise they differ.
RadioC1ash, don't get me wrong, I love SSD. It just doesn't offer considerable benefits at the moment. Maybe there is a bit of an improvement on seek time, battery performance, and stability. However, its not worth the extra money right now.
But, believe me, I got a watchful eye on the SSD market. I can't wait to replace these stupid mechanical drives!
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"Fix it 'til it Breaks."
Jacob - EiC & Director of Technology Mac Pro Quad 2.66 - 4GB RAM 160 GB SATA RAID 1 - 650 GB Storage Quad 19" Widescreen LCDs Accessorized to the Hilt