Questions about memory for a Lenovo Thinkpad T450s

[carver5678]

I'm shopping for memory for a Lenovo T450s, which has 4GB soldered to the motherboard and one available 204-pin DDR3 SO-DIMM socket, rated PC3-12800, 1600MHz, non-parity. I'm looking for an 8GB stick.

I care about reliability/longevity, performance, and price, in that order.

I assume that there is no value in getting a stick rated faster than PC3-12800, since the laptop wouldn't ever try to clock it faster than that. Is that correct?

Far a given clock speed, I assume the shortest CAS latency time would perform the best. Is that correct?

I've had very good results from Crucial in the past, and I'm inclined to go for a Crucial CT6942417 from crucial.com or a Crucial BLS8G3N169ES4 from Newegg, which is a few dollars less expensive and appears identical.

What do you think of those choices? Are there other units you would prefer over them?

 

[Emulex]

http://www.amazon.com/Crucial-PC3-1...=8-6&keywords=PC3-12800+1600MHz+DDR3L+so-dimm

works

so does CT6942405 , CT6942398 and CT6942385 if you can find it!

 

[carver5678]

Thanks for the pointer. That unit as CAS latency = 11, which means it takes 22% longer than the ones I'm looking at to respond to a Column Address Strobe (they have CAS latency = 9). The question is, will that additional speed make any difference to a Core i5-5200U CPU in a Thinkpad T450s?

 

[Emulex]

You know I doubt you would feel a difference but you can buy CL9 if you think it would make you feel better maybe 0.11% difference in benchmarks!

 

[hhhd1]

there is 16gb mdules that should work on that laptop to give you total off 20gb of ram, called intelligent memory.

if 8gb module is enough for you, then there are DDR3L:
crucial, samsung, kingston.

 

[coercitiv]

Thanks for the pointer. That unit as CAS latency = 11, which means it takes 22% longer than the ones I'm looking at to respond to a Column Address Strobe (they have CAS latency = 9). The question is, will that additional speed make any difference to a Core i5-5200U CPU in a Thinkpad T450s?

Your soldered memory is likely DDR3L 1600 CL11, use some diagnostics software to confirm. The model reviewed by Notebookcheck had CL11 memory.

 

[carver5678]

Your soldered memory is likely DDR3L 1600 CL11

So, if I have 4GB soldered + 8GB added, then any references within the first 8GB of the address space would be in dual-channel mode, limited by the slowest part. Is that correct?

As of now, this is just of academic interest, since I've just ordered the CL9 Crucial part; it was only $8 more than the CL11 part.

I'm still interested, just out of curiosity. I did a little bit of web searching and found some DDR3 timing diagrams. Clearly, a module running at 9-9-9-24 can get more work done per unit time than one running at 11-11-11-28, although you'd have to test actual apps to see if the difference would be human-observable.

 

[Hulk]

Funny you should ask. My t450s came in last week and I also ordered with 4GB RAM. I put in 8GB Crucial Ballistix Sport Single DDR3 1600 CL9 @ 1.35v.

CPUz shows the memory to be running at 800MHz NB 11-11-11-28 timings Command rate 1. Channel reads "dual" and shows 12GB. Not sure how that works exactly but I think the slower Lenovo memory is holding back the faster Crucial.

BTW I also installed a Transcend m.2 128GB SSD as the boot drive and it works like a charm. I'm using the 500GB mechanical drive for data.

 

[carver5678]

Well, that sounds like the final word on this topic - you're going to get 11-11-11-28 timing, even if you install memory that's capable of runnning faster (unless they switch to a different part for the soldered memory in the future). Thanks for the info.

I ordered the exact same SODIMM that you did. So we both could have gone with a CL11 version and saved $8.

 

[Hulk]

Well, that sounds like the final word on this topic - you're going to get 11-11-11-28 timing, even if you install memory that's capable of runnning faster (unless they switch to a different part for the soldered memory in the future). Thanks for the info.

I ordered the exact same SODIMM that you did. So we both could have gone with a CL11 version and saved $8.

That's true but as you noted in your original post you are looking for reliability above all. So am I. I would rather have the memory be rated above what it is running so if there is a little extra heat in the system, or a slight fluctuation in voltage it has a better chance of not crashing. I'll take that peace of mind for $8!

BTW, the laptop is really nice.

 

[coercitiv]

I'm still interested, just out of curiosity. I did a little bit of web searching and found some DDR3 timing diagrams. Clearly, a module running at 9-9-9-24 can get more work done per unit time than one running at 11-11-11-28, although you'd have to test actual apps to see if the difference would be human-observable.

The difference can be as high as 5-7% in isolated cases (file compression), but on most workloads it is virtually 0%. Info here.

 

[Bitkeeper]

That unit as CAS latency = 11, which means it takes 22% longer than the ones I'm looking at to respond to a Column Address Strobe (they have CAS latency = 9).

Sorry, but this is incorrect.
The latency is a 'number of clock-cycles'.
At DDR3-1333, the clock-frequency is 667MHz and one clock cycle is 1.5ns. Standard CAS-Latency for 1333 is 9. 9 x 1.5ns = total 13.5ns
At DDR3-1600, the clock-frequency is 800MHz and one clock cycle is 1.25ns. Standard CAS-Latency for 1600 is 11. 11 x 1.25ns = total 13.75ns

As you can see, the total time needed is nearly identical for 1333/CL9 and 1600/CL11. There is no "22% longer" as you state.

Each and every DRAM Chip, DDR1, DDR2 or DDR3, is specified with a minimum CL, tRP and tRCD time between 12.5 and 15ns. DDR3 typically has a minimum around 13ns. You can try and manually set lower CAS Latencies, but it could affect the stability of the system.

 

[carver5678]

As you can see, the total time needed is nearly identical for 1333/CL9 and 1600/CL11. There is no "22% longer" as you state.

I was comparing a 1600/CL11 part, suggested by user Emulex in post #2, with the 1600/CL9 parts mentioned in my original post.

 

[carver5678]

The difference can be as high as 5-7% in isolated cases (file compression), but on most workloads it is virtually 0%. Info here.

Thanks very much for that very helpful link!

 

[Bitkeeper]

I was comparing a 1600/CL11 part, suggested by user Emulex in post #2, with the 1600/CL9 parts mentioned in my original post.

Please be aware that DDR3-1600 @ CL9 is out of spec.
That would result in tRP/tRCD timings of 9 x 1.25 = 11.25ns which are outside of the specs of standard DDR3 chips.

I know that there are "overclocker-memories" on the market. These are built of standard Samsung, Micron, Hynix, but the manufacturers of those modules just do "trial and error" to see if they would still work at shorter CAS Latencies or higher clock rates than their official specifications.
This can be fine, but it is a certain stability and reliability risk... comparable to tuning cars.

Just look at datasheets of the chip-makers Micron, Samsung, Hynix and you will typically see 1066 @CL7, 1333 @CL9, 1600 @CL11 and 1866 @CL13. You will not be able to find any chips specified for 1600 @CL9 on the market. Companies offering modules with such speed just "try if it maybe works", put a heatspreader on them to make the original chip part numbers invisible and sell them. (or they buy the chips "unmarked").

 

[Hulk]

Please be aware that DDR3-1600 @ CL9 is out of spec.
That would result in tRP/tRCD timings of 9 x 1.25 = 11.25ns which are outside of the specs of standard DDR3 chips.

I know that there are "overclocker-memories" on the market. These are built of standard Samsung, Micron, Hynix, but the manufacturers of those modules just do "trial and error" to see if they would still work at shorter CAS Latencies or higher clock rates than their official specifications.
This can be fine, but it is a certain stability and reliability risk... comparable to tuning cars.

Just look at datasheets of the chip-makers Micron, Samsung, Hynix and you will typically see 1066 @CL7, 1333 @CL9, 1600 @CL11 and 1866 @CL13. You will not be able to find any chips specified for 1600 @CL9 on the market. Companies offering modules with such speed just "try if it maybe works", put a heatspreader on them to make the original chip part numbers invisible and sell them. (or they buy the chips "unmarked").

Well stated. I bought the "CAS9" for headroom. If the manufacturer is saying it'll work CAS9 then CAS11 should definitely work

 

[jaycub]

How are you guys finding the T450s running with the 12G as opposed to dual 16s (had Lenovo not soldered the 4G)?

I like the T40S, love the keyboard and of course the construction of the laptop itself.

Hulk, how did you install the SSD and then reinstall Windows onto it?
Does it come with discs? I'm assuming not?

 

[jaycub]

Bump?

 

[chubbyfatazn]

Hulk, how did you install the SSD and then reinstall Windows onto it?
Does it come with discs? I'm assuming not?

Not Hulk, but you can either order the disks from Lenovo or make a set of recovery disks yourself. Assuming you haven't blown away all the ThinkVantage stuff yet, there should be an option somewhere in the start menu that says "make recovery media" (or something like that). Either use that or find the option to do so in the Rescue and Recovery tool.

Come to think of it, you can just download an ISO of Windows (yes, you can do that) and apply the licence key that came with the laptop. You'd have to install the drivers afterward, but if you install the System Update tool it'll grab all the drivers you need and install them automatically for you.

 

[Hulk]

How are you guys finding the T450s running with the 12G as opposed to dual 16s (had Lenovo not soldered the 4G)?

I like the T40S, love the keyboard and of course the construction of the laptop itself.

Hulk, how did you install the SSD and then reinstall Windows onto it?
Does it come with discs? I'm assuming not?

Download the Microsoft "Mediacreationtool." This will allow you to download Windows 8.1 onto a USB Flash drive which can then be booted to from the t450s for a clean Windows install.

No need to order anything from Lenovo!

Also you don't even need to enter the license number as it will be "picked up" from the BIOS during the install.

Use a USB 3 flash drive and the install is pretty fast.

Also, once you get it installed with your primary apps I'd do a windows system image to an external drive so if you screw something up you can quickly pick up where you left off.