MP 1,1-5,1 Mac Pro 3,1 CPU downgrade - worth it?

[r6mile]

My new to me 3,1 MP is serving me fairly well (after some slight issues setting it up) and I've been using it with a low-power GTX 750Ti 2GB, which only uses 60W from the PCIe slot and is more than plenty to me.

Which has got me curious in reducing the power draw and heat output of this machine (which I know is a monster).

I currently have two 3.2GHz quad-core X5482s, which are the fastest for this machine but also run by far the most hottest at 150W TDP. Scrolling down the list however, I spot the 3.0Ghz quad-core E5472s that only run at 80W TDP. I don't imagine I'd ever notice the difference of those 200Mhz really.

The X5482s still also seem to command a premium and I could sell the two for £100 or so, whereas a pair of E5472s only cost £25.

Is this a silly idea? Grateful for any thoughts.

 

[Ludacrisvp]

if you have dual 3.2 from Apple (not aftermarket upgrade) the heatsinks used liquid metal for thermal paste which is super nasty to deal with. so you may not physically want to deal with that mess.

That said, another idea is do you need all 8 cores? you could cut power usage in half by removing one CPU, you don't need both to have a functional system.

Know that at idle the X5482 is going to run basically as cool / hot as the E5472 does for both temp and power consumption, so if you aren't taxing the system they aren't using that power anyways. (the CPU will speedstep down to lower clock rate when not needed)

 

[r6mile]

if you have dual 3.2 from Apple (not aftermarket upgrade) the heatsinks used liquid metal for thermal paste which is super nasty to deal with. so you may not physically want to deal with that mess.

That said, another idea is do you need all 8 cores? you could cut power usage in half by removing one CPU, you don't need both to have a functional system.

Know that at idle the X5482 is going to run basically as cool / hot as the E5472 does for both temp and power consumption, so if you aren't taxing the system they aren't using that power anyways. (the CPU will speedstep down to lower clock rate when not needed)

Thank you, this is extremely helpful. I believe they are the original 3.2s from Apple - I only just got this machine - so I will take your advice and keep it as they are. I also thought I should reapply thermal paste at some point, but this has dissuaded me of that idea too!

 

[Macschrauber]

There is a nvram setting

Boot-args="cpus=1"

 

[MacGarage]

This is interesting...I am using my Mac Pro 3.1 with dual 3.2 (that I bought new!) for a Security Spy and email server...so it is running 24/7. It does put out the heat which is great in the winter (it is in a heated outbuilding) but is noticeable in the summer.

I know the Mac Pro eats power...wonder what the heat and power savings benefits would be going to one processer?

 

[Ludacrisvp]

There is a nvram setting

Boot-args="cpus=1"

that doesn’t do what you think it does.
that will simply limit the os to use a single core from one cpu. It won’t shut down the other cores / cpus though.
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This is interesting...I am using my Mac Pro 3.1 with dual 3.2 (that I bought new!) for a Security Spy and email server...so it is running 24/7. It does put out the heat which is great in the winter (it is in a heated outbuilding) but is noticeable in the summer.

I know the Mac Pro eats power...wonder what the heat and power savings benefits would be going to one processer?

A great way to reduce heat would be to eliminate any spinning hard drives in the case. Hard drives generate a ton of heat.

 

[Macschrauber]

Ram does also generate heat and draw current.

If the cpu cores are limited then the heat and wattage of the processors are reduced as well. Worth at least some investigations before ripping one cpu.

 

[tsialex]

Ram does also generate heat and draw current.

If the cpu cores are limited then the heat and wattage of the processors are reduced as well. Worth at least some investigations before ripping one cpu.

Boot-args="cpus=1" don't change anything on the hardware side, just limit the kernel scheduler to one CPU. The second CPU will be drawing power and producing heat, albeit at idle - but idle power consumption of a Harpertown Xeon is absurdly high for today standards.

Since the memory controller is on the chipset, outside the processors, both memory banks will be active/working and drawing power normally.

 

[Ludacrisvp]

Can you drop down to using 2x 8gb DIMMs (One on each riser card) Or will that not be enough ram?

 

[Dayo]

The heatsinks on dual 3.2 from Apple used liquid metal

Does anyone know if it is necessary to use liquid metal on the 3.2 board?
Apple presumably had a reason for using this right?
I had previously upgraded my 2.8 to 3.2 on the 2.8 board but now changing the board to a 3.2 board.

Also, there are three heat sinks ... does the third one (near the RAM) need to be handled differently?

 

[tsialex]

The frequency of the northbridge is related to the base clock of the CPU, not on the multiplicator used by your Xeon. 2.8/3.0/3.2GHz all have the same 400MHz base clock (FSB) and the exactly same 1600MHz bus speed (QDR = FSB * 4), changing just the multiplicator.

Btw, the northbridge itself only changes clock if you install a Xeon with 333MHz base clock/1333 bus speed, like X5460 or X5450, instead of the usual 400MHz.

You can improve cooling for the northbridge if you want, since the air passing on the northbridge heatsinks from the Xeons heatsinks will be a little hotter than with a pair of 3.0GHz Xeons installed, so some people improve the thermal paste, but upgrading to a 3.2GHz Xeon won't change anything frequency wise with the northbridge itself.