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Mac Pro 1,1 with different 53XX Xeons

S

Spacedust

macrumors 65816
Original poster
May 24, 2009
1,008
161
We all know that stepping and voltage doesn't matter when replacing Xeons in our 2006 Mac Pros, but what about if you add different 2nd processor for example:

I got two E5345's now, and I would replace one of them with E5355. Will it work ?

It might be possible.

I started Orthos and stressed two cores of one processor and it started to work on max. speed 2.33 GHz, while the 2nd CPU is idle so it works on 2.0 GHz. This means Mac Pro mobo can handle different CPU speeds and the same time ;)
 
I've never heard of two processors operating at two different speeds on one motherboard, but know knows - it may be possible with the X5000 chipset. Would I do that personally? No - I'd match at least the speeds for both.

You could run different steppings, as long as they were the same type of processor (5355 - heck, you may even be able to mix an E5355 to an X5355, but again, I have not heard of that working before).

Peanut gallery? Any comments? ;-)

JP
 
There's a reason they don't sell systems like this; it won't work. On x86/x86_64 servers, the system won't even POST. Your test means that the Xeon processors can throttle separately. At the base though, the system sees processors with the same stepping, frequency, and multipliers.
 
It works on 5500 systems (Nehalem), but I dont recall reading if it does on anything else. Intel don't support it and neither do boardmakers, its just something that works but isn't reccomended.
 
Intel says they have to be the same speed. I bet it wouldn't hurt to try it tho and see what happens. My guess is that it either won't run or that it'll run at the slowest between the two.
 
I was allready surprised when someone got two same CPUs with different voltage working.

From a gut feeling I would also think that the board may throttle back the faster CPU if it works at all.
 
gugucom said:
I was allready surprised when someone got two same CPUs with different voltage working.

From a gut feeling I would also think that the board may throttle back the faster CPU if it works at all.
Click to expand...

I was really surprised when I lost my virginity...I DID throttle back though.
 
gugucom said:
I was allready surprised when someone got two same CPUs with different voltage working.

From a gut feeling I would also think that the board may throttle back the faster CPU if it works at all.
Click to expand...
Almost certainly to happen this way, as the voltage regs are operated by the same controller.
 
gugucom said:
I was allready surprised when someone got two same CPUs with different voltage working.

From a gut feeling I would also think that the board may throttle back the faster CPU if it works at all.
Click to expand...

That was me :) My Xeons are completly different steppings and voltages but works without problems. One is a little bit hotter, but no problems ;P
 
Spacedust said:
Clocks are the same 2x2.33 GHz
Click to expand...
Same P/N's (basic, i.e both are X5355), or are they different clocks per CPU?

I'm trying to verify if someone has two different clocked parts, and what they're running at. I'm presuming the VR's are controlled by the same chip, and would operate at the lower clocked part.
 
Funny you should ask... I've been reading up on this very topic. Xeon's are designed to be able to run at different voltages when used in the same system. That is if the motherboard will support, and apparently the this is the case on mac's, and most pc's seem to support this as well.

Frequency on the other hand has to be the same. This seems to be a limitation of the 5000x chipset. I'm not sure what would happen if you plug in processors with different FSB's as there is a mechanism for the processor to tell the motherboard what FSB it would like to see.

On the pc side of things, most overclocking of xeon's is messing with the pins to do this. Same as the BSEL mode people have tried to get working on the mp.

I'm almost betting that you could BSEL mod one processor to match the other, but not sure how well it would work as most seem to have problems when BSEL moding both processors. There's most likely something in the firmware limiting this... or more likely not supporting.

hyram
 
Wow! I think it would be really funny to have a 3.0 GHz and a 2.0 GHz in the same system. :D One time you do something it would be so slow and the next time you do it it might be really fast. :D
 
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