RAM speed / latency - diminishing returns?

[red454]

Current memory: Corsair CMZ16GX3M4A1600C9 Using two 4GB sticks on an ASUS Maximus IV Gene-Z.

Never had any problems. Standard XMP settings, no OC.

Getting ready to upgrade (ok, side grade) to a Maximus V Formula and i7-3770K.

The plan is to go to 16GB.

Generally at what point do you hit diminishing returns regarding memory speed and CAS latency?

Can you really tell any difference by going to higher speed or a lower CAS number?

Which leads to the final question - do I just buy some more of what I already have, or jump up a step or two? And if I jump up, I will be giving any "old" ram to my son, so it won't be wasted.

 

[tweakboy]

Ok Im the latency and DPC Latency guru here......

As bandwidth of RAM goes up so do the timings. For certain people that care about RAM latency. Say a 2400Mhz stick @ 11-11-11. If you downclock to say 1900Mhz and go 8-8-8 You wil have a snappier system. Your ram latency will be like 20ns or soo less. Test with AIDA64 FREE. Which means things happen faster its ok to lose some bandwidth. Also your upgrading just to go from 8 to 16GB

Why waiste money on a motherboard in Oct 2012 When a whole new tech Haswell CPU and new motherboard is coming out. save your money for that.

Then you can put 64GB if your mobo supports it. :wub:

What you need it for I don't know.

 

[Phynaz]

You aren't going to notice memory timings outside of synthetic benchmarks.

 

[dave_the_nerd]

You aren't going to notice memory timings outside of synthetic benchmarks.

There's probably the rare workload that will benefit. (I remember timings / latency making a difference when crunching SETI@Home back in the DDR1/Athlon days... when we actually used CPUs for distributed computing, .)

But I can't think of anything else where I've actually noticed it mattering. So any efficiency gains are probably not worth the time spent tinkering.

 

[red454]

Ok Im the latency and DPC Latency guru here......

As bandwidth of RAM goes up so do the timings. For certain people that care about RAM latency. Say a 2400Mhz stick @ 11-11-11. If you downclock to say 1900Mhz and go 8-8-8 You wil have a snappier system. Your ram latency will be like 20ns or soo less. Test with AIDA64 FREE. Which means things happen faster its ok to lose some bandwidth. Also your upgrading just to go from 8 to 16GB

Why waiste money on a motherboard in Oct 2012 When a whole new tech Haswell CPU and new motherboard is coming out. save your money for that.

Then you can put 64GB if your mobo supports it. :wub:

What you need it for I don't know.

Good info - thanks. As for my motivation, well, I am the tech / hardware guy at my house. Memory is about the only thing left that I haven't fooled with (learning). Wife and son don't care as much as I do about hardware and the latest and greatest tech stuff.

Anyway, my wife's computer is slowly dying. My son's computer is ok for now. And mine is ok too - but for Christmas, we decided to take his MB and CPU and give it to my wife (big upgrade for her). Then take my current MB / CPU and give them to my son (lesser jump for him). Of course, that leaves me in the market for an upgrade / side grade which makes it a win-win-win and everything gets recycled.

As for the memory, he runs several virtual machines and bumps the 8GB limit. I run SolidWorks and bump my 8GB limit, so if I am going to get a new MB / CPU and add a little memory, why not bump the memory up a notch, if it will make a difference. Doesn't seem to be a huge cost increase, however as fast as things run today, perhaps the memory speed jump is not really much to get excited about...

I have spent a lot of time looking into the Z77 vs. X79, and I agree with you about going to Haswell - but it is a timing thing for me (before Christmas). Plus, I like to wait and let a new platform (Haswell for example) mature a little. Let early adopters work the bugs out and deal with BIOS issues, BSoD's, etc.

And I really think that the Maximus V Formula and i7-3770K combo will be relevant for the next 3 years, especially with a nice GPU upgrade in a year or so.

 

[red454]

There's probably the rare workload that will benefit. (I remember timings / latency making a difference when crunching SETI@Home back in the DDR1/Athlon days... when we actually used CPUs for distributed computing, .)

But I can't think of anything else where I've actually noticed it mattering. So any efficiency gains are probably not worth the time spent tinkering.

Sort of what I figured - like trying to tell the difference in day to day usage between a 4.1 and 4.3 CPU overclock.

 

[dave_the_nerd]

Sort of what I figured - like trying to tell the difference in day to day usage between a 4.1 and 4.3 CPU overclock.

If I were you, and had the choice, I'd rather spend time and money on the "red 454" than the "black quad core."

Blasphemy around here, I realize.

 

[red454]

If I were you, and had the choice, I'd rather spend time and money on the "red 454" than the "black quad core."

Blasphemy around here, I realize.

True - but old red is all done. Just a parade car now...

http://www.cardomain.com/ride/365737/1972-chevrolet-impala

 

[kleinkinstein]

Ok Im the latency and DPC Latency guru here......

I just luv self proclamations! You must be so incredibly proud of yourself.

@OP, just run the math on the DIMMS you are considering and determine if the priceerformance is worth it.

Let's just do the math, the frequency is expressed in Hertz, which means "cycles per second". So, the DDR3 2133 will perform 2133 cycles a second while the DDR3 1600 will do, well, 1600. You, of course, know this.

Now the CAS latency is given in cycles. So, a CAS8 DIMM will take 8 cycles to respond and the CAS11, 11 cycles.

Now putting it all together - the DDR3 2133 CAS11 will take 11/2133 seconds, which is equal to 0.00516 seconds, to respond while the DDR3 1600 CAS 8 will take 8/1600, which is equal to 0,005 seconds, to respond. Thus, the 1600 DIMM is faster. For your dilemma, you're contemplating 0.000516 versus 0.00422 or timing difference of 0.00094 seconds! How fast are your reflexes and how long are you willing to wait for your memory to respond? Yes, I'm being an ass. You'll never ever see, feel or sense a difference.

You'll also want to carefully check the timings, since the higher the MHz the looser they are. I've seen 2133 DIMMS with 11-14-28-30, simply junk. As well as voltage, avoid anything higher than 1.5V. The only way many manufacturers get a respectable CAS at high MHz is to crank the voltage to 1.65V. Hence is why the 1.35V Samsung DIMMS are so smashing. Also, less DIMMs generally means less load to the memory controller. Therefore, 2x8GB is better than 4x4GB.

 

[red454]

I just luv self proclamations! You must be so incredibly proud of yourself.

@OP, just run the math and with the DIMMS you are considering and determine if the priceerformance is worth it.

Well, I would say that certainly puts it into perspective. Extra $ for humanly imperceptible improvements... But I will also add that this Corsair Dominator RAM is quite sexy: http://www.newegg.com/Product/Product.aspx?Item=N82E16820233282


http://redirect.anandtech.com/r?url...duct.aspx?Item=N82E16820233282&user=u00000687

 

[ShintaiDK]

http://www.anandtech.com/show/4503/sandy-bridge-memory-scaling-choosing-the-best-ddr3

 

[tweakboy]

Good info - thanks. As for my motivation, well, I am the tech / hardware guy at my house. Memory is about the only thing left that I haven't fooled with (learning). Wife and son don't care as much as I do about hardware and the latest and greatest tech stuff.

Anyway, my wife's computer is slowly dying. My son's computer is ok for now. And mine is ok too - but for Christmas, we decided to take his MB and CPU and give it to my wife (big upgrade for her). Then take my current MB / CPU and give them to my son (lesser jump for him). Of course, that leaves me in the market for an upgrade / side grade which makes it a win-win-win and everything gets recycled.

As for the memory, he runs several virtual machines and bumps the 8GB limit. I run SolidWorks and bump my 8GB limit, so if I am going to get a new MB / CPU and add a little memory, why not bump the memory up a notch, if it will make a difference. Doesn't seem to be a huge cost increase, however as fast as things run today, perhaps the memory speed jump is not really much to get excited about...

I have spent a lot of time looking into the Z77 vs. X79, and I agree with you about going to Haswell - but it is a timing thing for me (before Christmas). Plus, I like to wait and let a new platform (Haswell for example) mature a little. Let early adopters work the bugs out and deal with BIOS issues, BSoD's, etc.

And I really think that the Maximus V Formula and i7-3770K combo will be relevant for the next 3 years, especially with a nice GPU upgrade in a year or so.

No reason to get this motherboard because you didn't mention SLI or TRI SLI or Xfire.

Grab a consumer board like a ASUS P9 with a Ivy 3770k and 16GB kit and make sure to put SSD. Or else your gonna bottleneck this sexy system.

 

[red454]

http://www.anandtech.com/show/4503/sandy-bridge-memory-scaling-choosing-the-best-ddr3

Excellent - just what I was looking for. Thanks!

 

[red454]

No reason to get this motherboard because you didn't mention SLI or TRI SLI or Xfire.

Grab a consumer board like a ASUS P9 with a Ivy 3770k and 16GB kit and make sure to put SSD. Or else your gonna bottleneck this sexy system.

SLI or TRI SLI or Xfire - that is something I want to have as an option in the future, so the Formula board (along with all the ROG goodies) makes sense to me.

 

[tweakboy]

SLI or TRI SLI or Xfire - that is something I want to have as an option in the future, so the Formula board (along with all the ROG goodies) makes sense to me.

Oh sorry. Cuz I didnt see you mention it. Ok in that case stick with mobo alto its expensive I know....

 

[Revolution 11]

I second kleinkinstein's recommendation for Samsung's low profile 1.35v RAM. Low profile RAM with good overclocking potential at 1.35V? That signals quality RAM to me, even though there is little benefit to overclocking RAM in the first place but I appreciate the peace of mind.

If you are looking at other RAM choices, that's not a wrong thing to do. But don't get RAM because it looks "sexy" or has "sexy" heatsinks. Heatsinks are practically useless for RAM, vendors can put fancy pieces of metal on any generic RAm if they want, and if you are not overclocking the RAM, you are just wasting case space and restricting airflow for no reason. Get RAM because the price is better or if it can handle higher speeds at lower voltages, the only indicator of quality.

I would not overclock RAM anyway, the benefits are tiny compared to the risk of data corruption, etc, etc. Good RAM might be more stable, but run memtest anyway to make sure.

 

[red454]

I second kleinkinstein's recommendation for Samsung's low profile 1.35v RAM. Low profile RAM with good overclocking potential at 1.35V? That signals quality RAM to me, even though there is little benefit to overclocking RAM in the first place but I appreciate the peace of mind.

If you are looking at other RAM choices, that's not a wrong thing to do. But don't get RAM because it looks "sexy" or has "sexy" heatsinks. Heatsinks are practically useless for RAM, vendors can put fancy pieces of metal on any generic RAm if they want, and if you are not overclocking the RAM, you are just wasting case space and restricting airflow for no reason. Get RAM because the price is better or if it can handle higher speeds at lower voltages, the only indicator of quality.

I would not overclock RAM anyway, the benefits are tiny compared to the risk of data corruption, etc, etc. Good RAM might be more stable, but run memtest anyway to make sure.

Agreed - I will just stick with what I have and add some more of the same to it. The Corsair Vengeance stuff is currently $84 for 16GB.