RAM latency and frequency problem

[jasonycw]

I would like to know more about RAM speed and latency relationship

 

This is what I think so far:

 

When the speed it the same, lower the latency is better.

1600MHz C9 is better than 1600MHz C10

 

While with the same latency, higher speed is better.

1866MHz C9 is better than 1600MHz C9

 

But I am not sure which one is more important while looking for an upgrade. Latency or Speed???

 

But after Google for a while, I found an article showing some calculation of speed and latency.

(1/S)*L

S=speed(Hz)

L=latency

 

It said that lower the answer, better the RAM.

 

So I had do some calculation with some RAM kits that I am looking for.

 

1) Corsair Vengeance Pro CMY16GX3M2A2400C11A DDR3 2400MHz 16GB Kit (2x8GB):     (1/2400)*11 = 0.004583   HK$1750~=US$218.75

2) Corsair Dominator Platinum CMD16GX3M2A1600C9 DDR3 1600MHz 16GB Kit (2x8GB):   (1/1600)*9   = 0.005625   HK$1800~=US$225

3) Corsair Dominator Platinum CMD16GX3M2A1866C10 DDR3 1866MHz 16GB Kit (2x8GB): (1/1866)*10 = 0.005359   HK$1830~=US$228.75

4) Corsair Dominator Platinum CMD16GX3M2A1866C9 DDR3 1866MHz 16GB Kit (2x8GB):   (1/1866)*9   = 0.004823   HK$1910~=US$238.75

5) Corsair Dominator Platinum CMD16GX3M2A2133C9 DDR3 2133MHz 16GB Kit (2x8GB):   (1/2133)*9   = 0.004219   HK$1950~=US$243.75

 

Is this showing that (5) is the best and (1) follows as second. While there are quite some difference in price for (5) and (1) in my local store.

Which one is a better deal?

 

PS. I am using some cheap 8GB kit with 1600MHz and C11, which is about 0.006875

[Unhelpful]

If you are just doing gaming you probably wont notice a difference, go with the cheaper one.

[dizmo]

CAS 9 1866mhz is usually the sweet spot for price to performance.

Since where you are it's only $5 more you might as well go for 2133mhz.

[jasonycw]

CAS 9 1866mhz is usually the sweet spot for price to performance.

Since where you are it's only $5 more you might as well go for 2133mhz.

 

But isn't the 2400mhz C11 have a price to performance ratio??

[dragosudeki]

The higher speeds RAM and whatnot don't really change anything unless your APU uses your RAM... So I guess the price to performance ratio for higher speeds isn't worth looking at. I usually just get whatever is cheaper.

[Tea1337]

But isn't the 2400mhz C11 have a price to performance ratio??

Unfortunately, it doesn't work like that

[mgsstar]

What are you planning to use this system for?

[jasonycw]

Unfortunately, it doesn't work like that

So it doesn't matter whether I get the 1600mhz C9 or the 2133mhz C9 dominator platinum kit?

[jasonycw]

What are you planning to use this system for?

I use it for general web browsing, programming and gaming.

 

I found I need more RAM since I usually use up all the RAM when I web browsing and gaming. I usually have 10+ tab open while playing some RAM intensive game like BF4

[Tea1337]

So it doesn't matter whether I get the 1600mhz C9 or the 2133mhz C9 dominator platinum kit?

Not really, within the BIOS you can OC the ram to 2133, and it would be just the same.

[jasonycw]

Not really, within the BIOS you can OC the ram to 2133, and it would be just the same.

But I am not that comfortable with OC the ram manually, is there any noticeable difference between 1600mhz C9 and 2133mhz C9 RAM?

[Dmon]

But I am not that comfortable with OC the ram manually, is there any noticeable difference between 1600mhz C9 and 2133mhz C9 RAM?

No.

[Enderman]

youre wrong

C is actually not just 9, 10, or 11
its actually 4 numbers, thats why the ram is labeled like 9-9-9-24 or 11-11-11-27
some are even like 10-9-11-26
so your C is not accurate at all

also theoretically higher speed just means higher performance in benchmarks and a higher price

if you watch the techquickie video on it linus says that youre basically trading speed for latency, resulting in overall similar performance

you will never notice a difference between a low latency low speed or a high latency high speed ram in regular use

the only time you see a difference is in benchmarks or overclocking your ram

 

i would suggest just getting the lowest latency 1600mhz kit

plus its cheaper

[Grave]

Fasten your seatbelts, kids. I'm about to give you a crash course in RAM.

Column Address Strobe (CAS) latency, or CL, is the delay time between the moment a memory controller tells the memory module to access a particular memory column on a RAM module, and the moment the data from the given array location is available on the module's output pins. In general, the lower the CAS latency, the better.

In asynchronous DRAM, the interval is specified in nanoseconds. In synchronous DRAM, the interval is specified in clock cycles. Because the latency is dependent upon a number of clock ticks instead of an arbitrary time, the actual time for an SDRAM module to respond to a CAS event might vary between uses of the same module if the clock rate differs.

RAM frequency, AKA the clock speed of RAM, is the amount of data transferrable per clock cycle just like with everything else that has a frequency. In the case of DDR3 RAM, Sandy/Ivy/Older AMD CPUs have memory controllers built in which severely negate the benefits of the higher frequency DDR3 RAM (1600-1866+). While you might still see slight day-to-day performance gains, there are definitely insignificant ones even when comparing 2400mhz+ RAM CL9-11 to 1600mhz CL8-10 when gaming. That is because of A: the CPU's mem controller, and B: the Graphics card GDDR5 which is essentially faster DDR3-like RAM but dedicated to graphics processing.

Where faster RAM comes into play is with a proper CPU and professional/workstation workloads. It isn't likely to benefit you heavily unless you warp the timings on the RAM or will truly use all the frequency your RAM has. Situations like this would be 4k raw video processing, 3D rendering sometimes, basically anything that puts too much strain on the CPU's memory controller. By too much, I mean used up entirely. The equivalent of "WIDE LOAD" trucks for central processing units. I'm not 100% sure on this part, however.

There are also benefit limiting factors to getting higher frequency RAM such as L2/L3 cache size (and how you use each), your motherboard's capabilities, the RAM voltage your CPU can handle, the speed of your CPU and the CPU architecture itself. With APUs, they have graphics cores on the die so they can use your DDR3 as VRAM, or at least benefit from it in some cases as of now. Same goes for on-board video, but to a lesser extent as the graphics processing is quite a bit weaker. You could somewhat say the same for at least current Intel CPUs as well, since they have integrated graphics that are not so strong.

My take on it:

Generally speaking, 2133mhz CL9-11 240-pin DRAM is the threshold for general consumers and their frequency. Above that is generally better for workstation and harder daily processing, mostly for optimal efficiency especially when under heavier workloads. Now, that's not to say you should never buy 2400mhz RAM and this is because you can OVERclock and UNDERclock your RAM.

Overclocking RAM implies loosening the CAS timings and increasing the operating frequency of your RAM modules. Underclocking is the opposite; you tighten the timings and reduce clock speed to help stability. Speaking of stability, both over and underclocked RAM can affect overclocked CPUs and their stability. Be sure to run tests before you run into some potential issues using your computer.

The TL;DR is that underclocked RAM/a lower CL will benefit you in everyday use, lighter workloads and even in gaming more than an overclocked/higher frequency RAM, which would benefit you most in heavy workloads that stress the CPU's memory controllers. The former is somewhat true in APUs as well but more in favor of needing higher frequency RAM as there is no GDDR5 for the iGPU (at least with desktops).

Hopefully this completely eliminates confusion.

[Cubit481]

youre wrong

C is actually not just 9, 10, or 11

its actually 4 numbers, thats why the ram is labeled like 9-9-9-24 or 11-11-11-27

some are even like 10-9-11-26

so your C is not accurate at all

also theoretically higher speed just means higher performance in benchmarks and a higher price

if you watch the techquickie video on it linus says that youre basically trading speed for latency, resulting in overall similar performance

you will never notice a difference between a low latency low speed or a high latency high speed ram in regular use

the only time you see a difference is in benchmarks or overclocking your ram

 

i would suggest just getting the lowest latency 1600mhz kit

plus its cheaper

Hmmm...!!! THe difference is nearly negligible, and it will give similar real world performance, only the difference that comes is that with higher ram clock u can overclock ur cpu more effectively and if u are using ur integrated gpu, then it will give better physics score...that's it nothing more...

[Grave]

also theoretically higher speed just means higher performance in benchmarks and a higher price

if you watch the techquickie video on it linus says that youre basically trading speed for latency, resulting in overall similar performance

I'm pretty sure Linus is wrong about this in a way. I believe says this mostly because the performance gain between CL14 and CL9 is a theoretical 40-45% faster RAM in nanoseconds. In real-time, this is practically nothing in almost every real-world scenario. But if you can efficiently overclock your RAM, you can tighten the timings and lose less bandwidth than by just buying slower clocked RAM. This mostly happens with upping the voltage on your RAM, though.

Ideally, if you can find RAM with a lower CL at the same frequency, it's better. Otherwise, yeah, he's kind of right unless you're doing something along the lines of rendering the same amount of data CERN stores on a yearly basis, which is 25PB(Petabytes) of data, equivalent to roughly 22,350+ TB storage drives.

Edit: Fixed a sentence + added a bit more info.

Also, with DDR4 and HSA (from AMD and the Kaveri architecture), RAM will get a lot more clear as to why you'd want either a better CL or a higher frequency module. That or CL will be useless to modify. Trust me on this.

[mgsstar]

I use it for general web browsing, programming and gaming.

 

I found I need more RAM since I usually use up all the RAM when I web browsing and gaming. I usually have 10+ tab open while playing some RAM intensive game like BF4

I would get the Corsair Dominator Platinum CMD16GX3M2A1866C10 as games like BF4 will have some benefit with higher speeds and I don't think you will notice a difference between CL9 and 10.

[jasonycw]

Fasten your seatbelts, kids. I'm about to give you a crash course in RAM.

Column Address Strobe (CAS) latency, or CL, is the delay time between the moment a memory controller tells the memory module to access a particular memory column on a RAM module, and the moment the data from the given array location is available on the module's output pins. In general, the lower the CAS latency, the better.

In asynchronous DRAM, the interval is specified in nanoseconds. In synchronous DRAM, the interval is specified in clock cycles. Because the latency is dependent upon a number of clock ticks instead of an arbitrary time, the actual time for an SDRAM module to respond to a CAS event might vary between uses of the same module if the clock rate differs.

RAM frequency, AKA the clock speed of RAM, is the amount of data transferrable per clock cycle just like with everything else that has a frequency. In the case of DDR3 RAM, Sandy/Ivy/Older AMD CPUs have memory controllers built in which severely negate the benefits of the higher frequency DDR3 RAM (1600-1866+). While you might still see slight day-to-day performance gains, there are definitely insignificant ones even when comparing 2400mhz+ RAM CL9-11 to 1600mhz CL8-10 when gaming. That is because of A: the CPU's mem controller, and B: the Graphics card GDDR5 which is essentially faster DDR3-like RAM but dedicated to graphics processing.

Where faster RAM comes into play is with a proper CPU and professional/workstation workloads. It isn't likely to benefit you heavily unless you warp the timings on the RAM or will truly use all the frequency your RAM has. Situations like this would be 4k raw video processing, 3D rendering sometimes, basically anything that puts too much strain on the CPU's memory controller. By too much, I mean used up entirely. The equivalent of "WIDE LOAD" trucks for central processing units. I'm not 100% sure on this part, however.

There are also benefit limiting factors to getting higher frequency RAM such as L2/L3 cache size (and how you use each), your motherboard's capabilities, the RAM voltage your CPU can handle, the speed of your CPU and the CPU architecture itself. With APUs, they have graphics cores on the die so they can use your DDR3 as VRAM, or at least benefit from it in some cases as of now. Same goes for on-board video, but to a lesser extent as the graphics processing is quite a bit weaker. You could somewhat say the same for at least current Intel CPUs as well, since they have integrated graphics that are not so strong.

My take on it:

Generally speaking, 2133mhz CL9-11 240-pin DRAM is the threshold for general consumers and their frequency. Above that is generally better for workstation and harder daily processing, mostly for optimal efficiency especially when under heavier workloads. Now, that's not to say you should never buy 2400mhz RAM and this is because you can OVERclock and UNDERclock your RAM.

Overclocking RAM implies loosening the CAS timings and increasing the operating frequency of your RAM modules. Underclocking is the opposite; you tighten the timings and reduce clock speed to help stability. Speaking of stability, both over and underclocked RAM can affect overclocked CPUs and their stability. Be sure to run tests before you run into some potential issues using your computer.

The TL;DR is that underclocked RAM/a lower CL will benefit you in everyday use, lighter workloads and even in gaming more than an overclocked/higher frequency RAM, which would benefit you most in heavy workloads that stress the CPU's memory controllers. The former is somewhat true in APUs as well but more in favor of needing higher frequency RAM as there is no GDDR5 for the iGPU (at least with desktops).

Hopefully this completely eliminates confusion.

So, with that said, I am assuming getting higher speed ram is not as important as lower latency?

[Wingfan]

For what you are doing an 8GB 1600MHz kit would be the best option. 16GB would be overkill. I have 2133MHz rated RAM, and I don't see any difference between 1600 and 2133.

 

[jasonycw]

For what you are doing an 8GB 1600MHz kit would be the best option. 16GB would be overkill. I have 2133MHz rated RAM, and I don't see any difference between 1600 and 2133.

The problem is that I need an upgrade from 8GB to 16GB because I encounter lack of RAM issue a lot.

My lightweight usage need about 7GB and when I want to do anything additional, I need to close some other tabs or application first. That's why I want an upgrade.