Dual CPU's - Different models?

[Noel_inf1n]

I'm doing a school project where we are supposed do design a server suited for certain tasks and I was just wondering how duel-socket motherboards work. Can you use different processors as long as they have the same chipset or does the CPU's have to be the same model? I cannot seem to find any info on this anywhere.

Thanks in advance

//Noel

 

[mdd1963]

CPUs need to be same model/clockspeed within same generation, and, quite often, same revision, and, of course, approved to work in a multisocket mainboard....

(socket 2011-3, for instance, has a handful of dual socket mainboards, but, if trying to use more than one CPU, only 2xxx/4xxx/8xxx series Xeons may operate on them...and must be same model/revision, etc....)

 

[Snipergod87]

Typically the same model like 2x 2620v4's, not for example 2620v2+2680v4

I have done older servers (back in the day of single cores) when I had 1x 3.4Ghz CPU, and paired it with a 2.8Ghz CPU (same generation just a slower model) and it clocked them both down to 2.8Ghz.

 

[ragnar-gd]

>> Can you use different processors as long as they have the same chipset or does the CPU's have to be the same model?
You probably mean this:
>> Can you use different processors as long as they CAN USE the same chipset or does the CPU's have to be the same model?

Read this:

http://www.tomshardware.co.uk/forum/272899-28-different-processors-dual-socket-motherboard

 

[spdragoo]

http://www.tomshardware.com/forum/272899-28-different-processors-dual-socket-motherboard

https://serverfault.com/questions/650426/two-different-intel-xeon-e5-24xx-on-one-dual-socket-motherboard

If those are TL😀R for you, basically:
-- both CPUs have to have the same number of cores/threads (i.e. you can pair one 4C/8T CPU with another 4C/8T CPU, but you can't pair a 4C/8T CPU with a 6C/12T CPU).
-- both have to have the same TDP (i.e. you can't pair a 65W CPU with an 84W CPU)
-- both have to have the same QPI, or I/O bus (i.e. you can't pair a CPU with a 6.4GT/s QPI with a CPU that has a 9.6GT/s QPI)
-- both have to use the same RAM speeds (i.e. CPU #1 can't use DDR3-1866 if CPU #2 is only using DDR3-1600).

What will happen, though, is that the entire system will run at the speed of the slower CPU (similar to how, in SLI/CrossFireX, 2 GPUs will run at the speed of the slower of the pair). Which sounds like Intel's specs allow it more as a solution for customers that don't have identical CPUs available (i.e. scrounging usable CPUs from used servers), rather than for customers that are going to buy brand-new systems (because if your E5-2696 v4 is going to throttle your system, you'd be better off buying a 2nd one instead of pairing it with a Xeon E5-2699P v4).

As an FYI, it appears that the more cores a Xeon CPU has, the more likely it is that all of the Xeon models for that core/thread count have the same QPI speed -- for example, all of the 14C/28T & higher Broadwell-EP Xeons designed for dual-CPU motherboards all share the same QPI (2x9.6GT/s) & the same max RAM speed (DDR3-2400).