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I am currently looking at buying a HP Zbook Studio with an Intel Core i7-6820HQ, and I am looking at buying RAM separately. The best option on the HP website is 32 GB 2133 DDR4 SDRAM (2 DIMM) (probably CL15). Let's assume that price is irrelevant.

I was looking at this option: Vengeance Series 32GB (2x16GB) DDR4 SODIMM 2666MHz CL18 .

My questions are:

  • Is this memory compatible with the ZBook?
  • Will this memory run at 2666MHz or will the computer/cpu limits its use at 2133Mhz?
  • What will bring me more performances: the 2666Mhz CL18 or the 2133Mhz CL15?
  • How big the performance difference will be?
  • What will be the impact of 2666Mhz CL18 compared to the 2133Mhz CL15 in terms of energy consumption?
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Is this memory compatible with the ZBook?

Yes.

"Up to two SODIMMs, for system memory up to 32GB." - HP's website

Will this memory run at 2666MHz or will the computer/cpu limits its use at 2133Mhz?

I have never heard of RAM speeds being bound by a CPU, and even if it was IMO the performance increase is negligible in everyday tasks.

What will bring me more performances: the 2666Mhz CL18 or the 2133Mhz CL15?

I'm almost positive that the former will be more expensive for starters. Now let's do some math.

Ram Frequency is expressed in Hertz, which means "cycles per second". So the 2666 ram will perform 2666 cycles per second, while the 2133 will perform 2133 cycles per second.

Cas latency is given in cycles, thus CAS 18 means it takes 18 cycles to respond, while CAS 15 means it will take 15 cycles to respond.

Now to do some math.

  • 2666 RAM will take 18/2666 seconds to respond or about 0.00675 seconds.

  • 2133 RAM will take 15/2133 seconds to respond, or about 0.00703 seconds.

So in conclusion, the 2666 is faster.

How big the performance difference will be?

Around 0.00028 seconds.

What will be the impact of 2666Mhz CL18 compared to the 2133Mhz CL15 in terms of energy consumption?

Honestly, I don't think it matters. The ram plays such a small part in the energy consumption in the machine it's probably negligible.

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