This is my first post here. I have a HP dv3-2310ea laptop. It came with 3gb (2gb + 1gb) DDR3 PC3-8500 memory. It has an i3-350m processor.
I now want to upgrade to 8gb (2x4gb)
Crucial memscanner = PC3-8500 or PC3-10600 are supported.
HP manual = only PC3-10600 is recommended.
Intel (i3-350m webpage) = only DDR3-800/1066 (or PC3-6400 / PC3-8500) are supported.
For the 204pin SODIMM, I can only find the following available options:
PC3-8500 (1066MT/s) with cl=7 @533MHz = 13.14ns
PC3-10600 (1333MT/s) with cl=9 @667MHz = 13.5ns
Hence, i can purchase either of the two since the difference will not be noticeable. Both cost the same at Crucial.
However, my question is, if i purchase PC3-10600 but it was forced to operate at 1066MT/s (as suggested by intel), would it operate at latency of 7 or 9. Clearly if it runs at 9 (i.e @533MHz = 16.89ns) then i am better off buying PC3-8500?
I agree. My only thought was to buy as future proof ram as possible (esp since the price is the same). However if speed is limited down to 1066 but cl remains at 9 then the decision is a clear "no". On the other hand if cl drops to 7 whilst operating at the lower speed then its a win win situation?
I guess the basic question is whether CAS Latency is an intrinsic feature of the ram, i.e., does it remain the same irrespective of what speed it is operating at or does it vary?
Its usually determined by the SPD EEPROM on the memory module.
The SPD chip stores information such as the frequency, CAS# Latency, RAS# to CAS#, RAS# Precharge, tRAS, tRC, Command Rate and voltage for each Frequency that the memory module is capable of being operated at.
If you download and run CPU-Z and you look at the information on the SPD tab page you will get the idea of what I've described above.
Thanks for your response. Here are the CPU-Z screenshots. Does the SPD information relate specifically to the memory currently installed or does it mean that any installed memory could be operated at these timings? If it is the latter then going back to my original question, I could operate DDR3-1333 @533MHz and cl 7?
The SPD information is programed (i.e. burned) into the EEPROM chip on each memory module. Thats why you see the two different Timings Tables for your two different memory modules that you currently have installed.
The Memory tab page shows you what timings are currently being used by all of the memory modules installed.
You can operate memory that has a higher speed rating at a lower speed. The exact timings for the slower speeds, whatever they may be, should be in the module's SPD EEPROM chip.
I think I get it now. So it is all down to what options are permitted by the memory supplier.
So in my case, if the EEPROM of the DDR3-1333 memory is not programmed for lower latencies at lower speeds, then i will be stuck at the max speed allowed by intel (1066 in my case) but at the higher latency of 9?
If the above interpretation is correct, then DDR3-1066 would be my best option (as you had suggested earlier)?
I would think the CAS latency would be programmed into the SPD chip as 7 for 533 MHz on the DDR3 1333 (PC3 10600). To be sure you can contact the manufacturer and ask them what the exact timings are when operating their DDR3 1333 (PC3 10600) modules at 533 MHz.