Thinkpads Forum

Hi!

Today I had to add some more memory to a T400s. It was originally with 2GB PC3 8500 DDR memory (Elpida modules).
I ordered the new modules, they arrived. After the first start (when the new modules were in the notebook) I realized that the new Kingston modules are PC3 10600 DDR3 modules with CL9 latency. They are working in the notebook.

Do you know any incompatibility about PC 10600 DDR3 modules in T400s?
Shall I send them back or they will work fine?

They will work, but will downclock to pc8500 speed.

what about the latency?. How is it adjusted?. Does one get less latency or more?.

Hi, latency will be equal or less, as long as you are reducing the speed of the modules, so no problem here. The modules do have an SPD which programs them to work with the proper latency according to the actual bus speed. This data can be overriden by BIOS, which only does it because the user did it manually (not the case, can not be done on thinkpad BIOSes), or to improve, so in any case you are safe...

are you saying that the memory modules adjust the wait cycles based on the FSB?..
I get the kingston 10600 alitte cheaper here, I didnot settle for it only because it was exhibiting 9 cycles instead of 7 on its packaging.The salesboy was scratching his head for losing the sale to
another dealer next door.

are you saying that the memory modules adjust the wait cycles based on the FSB?..

Yes.. well, almost... the system adjusts the memory timings according to the memory bus speed (which does not always equal the fsb speed), normally as per what the SPD on the memory says. The SPD is a litthe table which lists the different timing characteristics given certain frequencies. You can see this with several utilities (for a popular one, look into the 'SPD' tab of the CPUZ utility).