Xeon X5365 CPUs are top of the Clovertown range and run at maximum FSB 1333MHz. To apply BSEL/VID mod overclocking, you would need:
- CPUs with lower FSB than the highest supported by the chipset (here, Intel 5000X which supports FSB 1066 & 1333)
- CPUs with a higher max. multiplier than your current X5365 models
You evaluate your gain by calculating the target max. CPU speed, i.e. multiplying max. multiplier by FSB/4 (because FSB is quad-pumped). For instance, your current X5365 CPUs run at 3.0GHz, a speed obtained by multiplying 1333/4 by max. multiplier 9. If the new CPUs have a large L2 cache, this can significantly improve performance too.
In the Clovertown series, the only models with a lower FSB and a higher multiplier would be the Xeon E5350/X5350: FSB 1066 + max. multiplier x10. In theory and if they exist (because they're not listed on Intel Ark), you could therefore opt for those CPUs and overclock them to FSB1333 through pinmod/voltmod to obtain CPUs @3.33GHz. That would be a 25% increase over their original speed but a mere 11% over your existing CPUs, making the exercise hardly worthy in my opinion.
MacPro1,1 shipped with WoodCrest dual-core Xeon CPUs (best CPU was Xeon 5160). You've got Clovertown quad-core models @3.0GHz (as in the MacPro2,1) and, apart from the highly unlikely upgrade I've just mentioned above, that's the best you can get on this 11yr-old machine. Afaik, Harpertown Xeon CPUs (last LGA771 series, up to FSB 1600) as fitted to MacPro3,1 (Intel 5400 chipset) are not compatible with MacPro1,1/2,1. I understand that Intel 5000X chipset would support them but MacPro1,1/2,1's EFI/Firmware does not.
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