The SONNET HARMONi G3 pushes the performance of your "original" iMac to stratospheric performance levels, enabling you to enjoy the video editing capabilities of the latest systems. Employing a powerful 600MHz IBM PowerPC G3 processor with on-chip 256K Level 2 cache operating at full processor speed, HARMONi will transform your iMac with a performance boost of up to 2.5x or more. 3 year warranty

REVIEWS:
1) Does what it"s supposed to do: A great product for breathing life into the old G3 iMacs. If you love your iMac, perhaps want to donate it to the kids, this will keep the Mac going. I installed one into my son"s 333MHz iMac with all the results promised. The OS was definitely speedier, and the Firewire port supported an external CD-RW perfectly. OS 10.2.8 runs very well. You want to be confident in your computer modding skills, as you take out everything but the motherboard, the PSU and the CRT to install this.

Expensive, but a good move for someone that wants to keep the old iMac around. Also, Amazon states that it"s unavailable, but www.sonnettech.com still has it in stock. Enjoy.