First off..
Why would someone who owns a single-quad core mac pro use a dual core chip to begin with? Isn't that a sheer waste of money? the x5580 is roughly the same thing as the w3580 except it supports dual channel qpi. And the 2nd qpi would be disabled on the single-quad core because, well - one cpu only.
Dual w3580 will not work in the dual because the processor is a single-qpi based chip.
Why would someone who owns a single-quad core mac pro use a dual core chip to begin with? Isn't that a sheer waste of money? the x5580 is roughly the same thing as the w3580 except it supports dual channel qpi. And the 2nd qpi would be disabled on the single-quad core because, well - one cpu only.
Dual w3580 will not work in the dual because the processor is a single-qpi based chip.
This is an old post of mine but the question has been answered a few times. It won't work due to the microcode in the BIOS not supporting it, and the stepping is different (B1 vs. D0). So, I know this now, it just won't work at all. Dual W3580 has been proven to work and dual X5580 has been proven to work too. That's about as high as you can go with the dual Mac Pro...dual 8-core 3.33GHz. The Quad Core upgrade has been well documented too...you can do i7 975, W3580, or X5580 for roughly the same effect, different price levels for the processors. The 12-core upgrade simply won't work on any Mac Pro, as of now. Again, since my post, it's been well documented on other posts and I got the answer to my question. Thanks!