Formula for comparison of RAM

[Chuck Comet]

Hi, all...

 

So, I am down to the Memory choice for my build. I have looked and looked at 2x8GB dual channel sets, and have come up with a formula (of sorts... I'm no mathematician) that is helping me choose RAM. What do you think about it as a comparison tool?  

 

Value = CAS / Speed x Price (where CAS is the first timing, Speed is in gHz and price is current available in USD)

 

For example...

 

DDR4-2133 at 15CAS for $153   gives a Value of 1075.95 (15/2.133 x 153)

DDR4-2400 at 15CAS for $164   gives a Value of 1025 (15/2.4 x 164)

DDR4-2666 at 15CAS for $170   gives a Value of 956.49 (15/2.666 x 170)

DDR4-3000 at 15CAS for $198   gives a Value of 990 (15/3 x 198)

 

DDR4-2133 at 14CAS for $175   gives a Value of 1148.62 (14/2.133 x 175)

DDR4-2400 at 14CAS for $145   gives a Value of 845.83 (14/2.4 x 145)

DDR4-3000 at 14CAS for $240   gives a Value of 1120 (14/3 x 240)

 

DDR4-2400 at 10CAS for $230   gives a Value of 958.33 (10/2.4 x 230) This is the Corsair Dominator Platinum

DDR4-3200 at 14CAS for $189   gives a Value of 826.88 (14/3.2 x 189) This is the Team Dark Pro which was my choice, but they are sold out at that price (another You Snooze You Lose moment for me). 

 

This formula doesn't take into account the full timing, of course (15-19-19-36 is WAY different than 15-15-15-30, for example).  It also doesn't really take the performance increase into account (It would be a difficult decision to choose between a 2666/15 for $170 and a 2400/10 for $230 because the price versus performance, even though the Values are only 1.84 apart). 

 

I'm sure there are a ridiculous amount of errors in both my math and my thinking, and I'd love to have y'all point them out and get me thinking better about my coming decision. Be kind... I'm a Newb. :-)

[porina]

I think that's over-complicating things somewhat. Just pick something fast-ish in budget and looks nice. Done.

[Princess Luna]

4 minutes ago, porina said:

I think that's over-complicating things somewhat. Just pick something fast-ish in budget and looks nice. Done.

GSkill Trident Z is always the answer, Samsung Modules and Dies, good built quality, most pretty looking... total win win do not regret mine one bit... did not take the RGB one though as it was overpriced lets be honest but after I found the static White one damn it looks awesome :3

[Schrodingers Kat]

AnandTech has a rough formula for working out ram performance, which is Speed/Cas in mHz. Eg 2400mHz at CAS 15 = 160. However really just aim for what you can afford within your build, minimum should be 2400 mhz at any timings unless its a really budget build. After that aim for 3000 or 3200. Remember any overclocking mobos will allow for overclocking ram also so you can somewhat help middling ram timings later with an overclock at higher ram voltage. 

[MageTank]

10 minutes ago, Chuck Comet said:

Hi, all...

 

So, I am down to the Memory choice for my build. I have looked and looked at 2x8GB dual channel sets, and have come up with a formula (of sorts... I'm no mathematician) that is helping me choose RAM. What do you think about it as a comparison tool?  

 

Value = CAS / Speed x Price (where CAS is the first timing, Speed is in gHz and price is current available in USD)

 

For example...

 

DDR4-2133 at 15CAS for $153   gives a Value of 1075.95 (15/2.133 x 153)

DDR4-2400 at 15CAS for $164   gives a Value of 1025 (15/2.4 x 164)

DDR4-2666 at 15CAS for $170   gives a Value of 956.49 (15/2.666 x 170)

DDR4-3000 at 15CAS for $198   gives a Value of 990 (15/3 x 198)

 

DDR4-2133 at 14CAS for $175   gives a Value of 1148.62 (14/2.133 x 175)

DDR4-2400 at 14CAS for $145   gives a Value of 845.83 (14/2.4 x 145)

DDR4-3000 at 14CAS for $240   gives a Value of 1120 (14/3 x 240)

 

DDR4-2400 at 10CAS for $230   gives a Value of 958.33 (10/2.4 x 230) This is the Corsair Dominator Platinum

DDR4-3200 at 14CAS for $189   gives a Value of 826.88 (14/3.2 x 189) This is the Team Dark Pro which was my choice, but they are sold out at that price (another You Snooze You Lose moment for me). 

 

This formula doesn't take into account the full timing, of course (15-19-19-36 is WAY different than 15-15-15-30, for example).  It also doesn't really take the performance increase into account (It would be a difficult decision to choose between a 2666/15 for $170 and a 2400/10 for $230 because the price versus performance, even though the Values are only 1.84 apart). 

 

I'm sure there are a ridiculous amount of errors in both my math and my thinking, and I'd love to have y'all point them out and get me thinking better about my coming decision. Be kind... I'm a Newb. :-)

This formula simply doesn't work because clocks and primary timings tell you very little about actual real world performance. High frequencies and tight primaries mean nothing if tertiary timings are loose enough to the point in which you are losing bandwidth efficiency. Spend less time comparing the clocks and timings, and more time comparing the individual IC's within the kits. If you need resources for finding which IC's are in which kit, there have been strides to find the various IC's each kit has after Ryzen launched. Refer to the page below for information as to which kits have which IC's, and from there, cross reference those IC's against HWbot's memory OCing database to determine which are the best for performance. Right now, Samsung B-Die is king for both AMD and Intel.

 

https://www.reddit.com/r/Amd/comments/649ay8/ram_collection_thread_please_post_your_ram/

 

A lot of your ram's performance depends entirely on your IMC and board as well. Simply comparing the stats you find on marketing pages for various DIMM's won't give you any real information as to how it's going to perform for your system. You and I can buy the exact same kit of memory at the exact same time from the exact same production line, and still end up with drastically different performance depending on how our IMC and motherboards train the tertiary timings. From the time I spent OCing memory, I can say this: You are better off buying memory that you like (both in terms of price and aesthetics) and overclock the kit manually, rather than relying on any XMP marketing data. You will not only save money, you will end up with a faster system by the end of it. 

1 minute ago, Schrodingers Kat said:

AnandTech has a rough formula for working out ram performance, which is Speed/Cas in mHz. Eg 2400mHz at CAS 15 = 160. However really just aim for what you can afford within your build, minimum should be 2400 mhz at any timings unless its a really budget build. After that aim for 3000 or 3200. Remember any overclocking mobos will allow for overclocking ram also so you can somewhat help middling ram timings later with an overclock at higher ram voltage. 

That formula still doesn't work in the grand scheme of things for the reasons I mentioned above in my post. Frequency / CAS only tells you of absolute potential, it does not tell you what you are actually capable of getting. Tertiary timings dictate bandwidth efficiency, and they are the timings that allow you to actually get close to reaching that potential. They are also entirely dependent on IC quality, board quality (trace topology), and IMC quality. 

[Chuck Comet]

9 minutes ago, MageTank said:

This formula simply doesn't work because clocks and primary timings tell you very little about actual real world performance. High frequencies and tight primaries mean nothing if tertiary timings are loose enough to the point in which you are losing bandwidth efficiency. Spend less time comparing the clocks and timings, and more time comparing the individual IC's within the kits. If you need resources for finding which IC's are in which kit, there have been strides to find the various IC's each kit has after Ryzen launched. Refer to the page below for information as to which kits have which IC's, and from there, cross reference those IC's against HWbot's memory OCing database to determine which are the best for performance. Right now, Samsung B-Die is king for both AMD and Intel.

 

https://www.reddit.com/r/Amd/comments/649ay8/ram_collection_thread_please_post_your_ram/

 

A lot of your ram's performance depends entirely on your IMC and board as well. Simply comparing the stats you find on marketing pages for various DIMM's won't give you any real information as to how it's going to perform for your system. You and I can buy the exact same kit of memory at the exact same time from the exact same production line, and still end up with drastically different performance depending on how our IMC and motherboards train the tertiary timings. From the time I spent OCing memory, I can say this: You are better off buying memory that you like (both in terms of price and aesthetics) and overclock the kit manually, rather than relying on any XMP marketing data. You will not only save money, you will end up with a faster system by the end of it. 

That formula still doesn't work in the grand scheme of things for the reasons I mentioned above in my post. Frequency / CAS only tells you of absolute potential, it does not tell you what you are actually capable of getting. Tertiary timings dictate bandwidth efficiency, and they are the timings that allow you to actually get close to reaching that potential. They are also entirely dependent on IC quality, board quality (trace topology), and IMC quality. 

Dude... that's the single best thing that I have seen posted on this site. BS like, "Just pick something fast-ish in budget and looks nice. Done." does us all a disservice. Your response taught me something, and now I can take my personal research further (and again, my research doesn't hold a candle to most). Thanks!

[MageTank]

Just now, Chuck Comet said:

Dude... that's the single best thing that I have seen posted on this site. BS like, "Just pick something fast-ish in budget and looks nice. Done." does us all a disservice. Your response taught me something, and now I can take my personal research further (and again, my research doesn't hold a candle to most). Thanks!

While not entirely complete, I do also have a memory overclocking guide in my sig if you'd like to read a novels worth of information on the subject. I am also working on a mobile SO-DIMM overclocking guide, once I receive my laptop and get a custom bios flashed on it. Good luck with your ram selection.