Thinkpads Forum

Hi Folks,

t400 memory has been discussed here before (http://forum.thinkpads.com/viewtopic.php?f=45&t=73702), but i was hoping to re-open the topic. I'm looking for a 4gb module for my t400, and know that I need ddr3 pc3-8500 204 pin non-ecc non-buffered. However, there is a range of CL's out there, and who knows what else differs in these modules. Is lower CL always better, or is there a point at which it doesn't matter? It also seems important to have the same specs amongst modules in order to get DDR performance, though I'm not sure what specs have to match up.

Any thoughts? I'm looking at http://www.ewiz.com/detail.php?p=W1066SB4GV&c=pw# , to start.

Thanks,
Allie

t400, 2764-CTO, T9600 2.8 GHz, Win 7 Pro x64

CPU-Z output:
Chipset
-------------------------------------------------------------------------
Northbridge Intel GM45/GM47 rev. 07
Southbridge Intel 82801IM (ICH9-M) rev. 03
Graphic Interface PCI-Express
PCI-E Link Width x16
PCI-E Max Link Width x16
Memory Type DDR3
Memory Size 2968 MBytes
Channels Dual, (Symmetric)
Memory Frequency 531.9 MHz (1:2)
CAS# latency (CL) 7.0
RAS# to CAS# delay (tRCD) 7
RAS# Precharge (tRP) 7
Cycle Time (tRAS) 20
MCHBAR I/O Base address 0x0FED10000
MCHBAR I/O Size 4096

I would start by getting a module with a frequency that matches your front side bus. If you get something like DDR3 1333 and your FSB is 1066 MHz, you're not gaining anything. After that I would look for low latency. If you want to compare modules with different specs you could do this:

1/(freqency) * CL = some value (the lower the value the faster it makes one cycle)

Ex:
DDR3 1333 with CL 9
1/1333 * 9 = 0.00675

DDR3 1066 with CL 7
1/1066 * 7 = 0.00656 (theoretically the better performer, but not by much)

Of course, after you get the specs you want, you should check that it's compatible with your T400. Most memory manufacturers should have a list of which models are compatible with which machines.

thanks superego. So, the CL is negotiable then. On the other hand, saying that I must check that the memory is "compatible" with the t400 defeats the purpose of this thread. The point is to know what memory IS compatible, so I can buy the correct memory that will work well on the cheap.

So - if i get 204 pin SODIMM non-ecc non-buffered CL(4-9) 4gb 1066 MHz RAM, is that "compatible"? Or are there other things I must take into account?

albo,

Sorry, I didn't make myself clear. The specs you have listed (204 pin SODIMM non-ecc non-buffered CL(4-9) 4gb 1066 MHz RAM) will work....that module is compatible with your t400.

What I was trying to explain (and failed at) is that most memory manufacturers have a either a list or web-based system that allows you to enter the make and model of your system and it spits out a list of modules that have been tested on that particular computer. Here's the site for Super Talent (the brand you posted):

http://www.supertalent.com/tools/memoryFinder.php

Personally, if I was shopping for laptop RAM and I happened across a good deal but the module wasn't listed for my system, I'd probably still go with it (assuming the major hardware specs like pin, non-ecc, non-buffered, etc, were satisfied first). If you find out the RAM doesn't work well with your laptop you can always return it. On the other hand, if I was building a system from scratch then I would only go with RAM that has been tested for the specific motherboard I've chosen.

Hope that clears things up.

cool - thanks superego. appreciate the help!

Need some help to clarify the memory specs for T400: It´s possible to install 4GB RAM or more in all T400 models, as stated on http://www.intel.com/design/chipsets/em ... /index.htm?

1066 MHz front-side bus; up to 8 GB 667/800 MHz DDR2 or 800/1066 MHz DDR3 SO-DIMM system memory; Mobile Intel® Graphics Media Accelerator 4500MHD; PCI Express* graphics support

(from Intels website)

you can install up to 8GB, in 2 4GB chips. sounds like some folks mod their bios to allow up to 16GB? Not sure - just saw someone imply that somewhere - can anyone confirm that?

Sure you can put 2 4Gb sticks to make it 8 Gb, but the cost of 4 Gb sticks is very hight right now.

around 2 Benjamins.