Can MacPro 2006 run with just one CPU (x5365)?

[lbodnar]

I am waiting to upgrade my 2006 MacPro from 2x2.66 duals (5150) to 2x3.0 quads (x5365.) So far I have received my 1st X5365 and fishing for the second one.

Can I replace two 2.66 duals with one 3.0 quad for now? I know that this Xeon configuration is possible in theory but have anybody tried this on MacPro1,1 ? What happens with performance?

Also, I know that Intel does not officially guarantee operation when mixing different CPUs but has anybody tried mixing one 5365 and one 5150? I can't believe nobody tried this yet?

 

[gugucom]

We had the discussion half a year ago and I learned that you can run one CPU. So you should try this. I don't think there is a chance to damage your system.

If you have radically different configs I would be more sceptical but still little chance that it would do damage. The risk of getting undocumented errata increases with every step away from the standard config.

 

[lbodnar]

We had the discussion half a year ago and I learned that you can run one CPU. So you should try this. I don't think there is a chance to damage your system.

If you have radically different configs I would be more sceptical but still little chance that it would do damage. The risk of getting undocumented errata increases with every step away from the standard config.

Thanks, gugucom.
Talking about seemingly standard config... Anybody running X53xx on their original MacPro1,1 should know that there is no microcode update in the EFI there! And even MacPro2,1 EFI has only microcode data for CPUID 0x6F7 (X5355 SL9YM SLAC4) No microcode data for X5355 SLAEG and X5365 SLAED!

I am not a CISC person so I don't know what errata each microcode actually fixes in each stepping...

 

[lbodnar]

We had the discussion half a year ago and I learned that you can run one CPU.

I can't find this discussion...

So what happens to CPUB heatsink in such case - do I disconnect fan and take it out or leave connected over an empty (protected) socket?

 

[gugucom]

I can't find this discussion...

So what happens to CPUB heatsink in such case - do I disconnect fan and take it out or leave connected over an empty (protected) socket?

https://forums.macrumors.com/posts/8200032/

Yes, I would run the empty socket without heat sink.