16GB of RAM: 4x4GB or 2x8GB

I'm thinking of bumping my RAM to 16GB (before you ask, yes, I've needed more before with some code I was running, not for gaming). This would be for a Sager NP9150 (Clevo P150EM)

I currently have 2x4GB of Corsair Vengeance 1.5V 1600MHz Cas Latency 9 RAM.

I'm weighing out two options. Performance is very important to me, whichever would technically be the higher performer would be what I want. But battery is also important. If 4 sticks will suck up a noticeable amount of extra power, then that'd be a problem too.

I'm thinking of just getting a couple of the same sticks which would run me $90 and use all 4 dimms. I don't need anymore more room to upgrade later so I don't mind using all 4. The other thought, is if performance is better or battery life is better, is getting 2x8GB of HyperX PnP since I can also get 1.5V 1600MHz CL9 in that variety and it would cost $140 (and I'm sure I could sell my current sticks for $40-50). [For Corsair 2x8GB, I'd either have to get CL10 sticks or 1.35V that is backwards compatible to 1.5V for CL9 but both are more expensive than the HyperX]

So which would you recommend? Thanks!

 

If you don't need the extra room for expansion later, then I see no reason to go with the more expensive options. Just get two more of whatever you've got and call it a day. I don't think you'll notice an impact on battery, and performance should also be the same.

 

Ok if we are saying pure technical here the 2x8gb may be a better performer. So here is goes;

1.) cas timing is always important. You want the lowest possible, With DDR3 I think with either 4gb or 8gb you can get them the same.

2.) Command rate, now there is no guaranties here but 2 sticks has a better chance to allow a 1T rate than 4 sticks. So long as you can get the rate as 1T you are fine. a lot of systems, especially with cheaper ram, will relax from 2 sticks at 1T to 2T so that 4 sticks will work without issues.

Now again this all from a technical standpoint.

 

I would go with 2x8GB SoDimms. Test them overnight and if they pass sell the old ones.

As TANWare states: they are technically better - but they are also the better long term buy too.

Two sticks of RAM will behave better than 4 sticks of RAM every time. And as this will cost you about the same in the end: it is the best way forward imo.

 

This one is easy to choose:

x4 4GB sticks will give you better performance (technically) though we are talking like 2-3% at best and obviously better price since you already have 2x4gb sticks. However, no further expansion capacity later.

x2 8GB sticks will give you better battery life (again 2-5% at best) depending on the technology of the 8gb sticks (the newer ones are usually on smaller lithographies so you save power by the better process node in addition to having fewer DIMM modules to power),
To put in to perspective,Tweaktown found that 1x8gb 1600mhz CL11 1.35V (newer process node) will give 6% more battery life than 1x4gb 1600mhz CL11 1.5V (older process node).
Patriot Memory for Ultrabook PC3-12800 8GB LoVo SODIMM Review - Benchmarks - Test System Setup and Battery Life Test
However performance will be slightly slower (we're talking very very small, maybe slightly looser secondary timings on the more advanced sticks). Obviously, cost is greater. As for expansion, I would double check if your notebook motherboard and CPU can support 32GB of RAM as this is not guaranteed.

 

Umm I think 4x4GB would actually give lower performance (unless you have a quad channel chipset), because you'd be running 2 banks per channel as opposed to 1 bank per channel, and that puts higher strain on the memory controller inside the CPU.

 

Not necessarily (from a latency point of view), I think the banks are actually accessed in parallel, the additional stress usually reduces the stability of the memory bank at a given clockspeed/latency combination. I believe the reason Quad Channel is perceived as faster (besides from the obviously wider interface) is because it can take more stress before instability forces the system to run the RAM banks at lower clockspeeds/looser latencies.

 

Performance should be the same. One thing though is that 4GB modules come in higher performance varieties than 8GB modules.

Your plan to buy two more 4GB sticks is fine. You aren't losing out on anything and are saving some money.

However, also keep in mind that there is a third option. You can buy 2x8GB memory modules AND keep the 2x4GB modules you already have, for a total of 24GB of memory. It might be overkill for what you do, but the option is there.

 

If you run Command rate at 2T vs 1T you are introducing latency to enhance stability. Not all RAM is created equal so again technically this is something to consider. Problem is most RAM will not advertise command rate.

 

So after some brief searching online, I noticed that most of the Command Rate articles are old relating back to DDR2 and DDR days while DDR3 says timings are less important these days. I just checked my current 2x4GB set in CPUZ and it shows 9-9-9-24-1T timings. I have no intentions of overclocking or modding my BIOS to do so, but do 4 dual channel sticks typically default to 2T or something or is this just a different timing seen from manufactures regardless of number modules used?

 

JEDEC profiles for 4gb sticks at 1600mhz are typically 1T. 8GB sticks tend to have 2T so that they are still stable at CL 11-11-11-28. The memory controller is programmed to utilize the slowest latency settings (i.e. the speed of the slowest RAM module).
As for the difference? My laptop has a Modded BIOS that allows alteration of the Command Timing, I can tell you it is very very miniscule even at the sluggish speeds of 1600mhz 11-11-11-28-2T. But the added OC headroom allows certain combinations such as 1866mhz at 10-10-10-28 or 2133mhz at 11-11-11-32 which were crazy back about 2yrs ago for SODIMM, mind you this was back when the 20nm Samsung RAM was just rolling off the Fab lines.

 

On my machine the command rate is locked to 1T, so 4GB or 8GB sticks both run at 1T, regardless of speed. Haven't had any issues thus far.