Thinkpads Forum

hey guys
i was planning to buy extra ram for my x61 7675-H7U w/ T8100 processor

like in the subject line, what is the difference between all those pc2's..the price seems very marginal between those rams..is it that the 6400 is faster or better or something like that..

and also which one of those are compatible with my x61..

thanks in advance!!

The number after PC2 is the memory bandwidth, i.e. 5300 means 5300 MB/s memory bandwidth (approximately). AFAIK PC2 5300 and PC2 5400 are actually the same type, only labeled differently by different manufacturers (due to rounding errors), these modules are 667 MHz. PC2 6400 is 800 MHz but will downclock to 667 MHz in your machine due to the Santa-Rosa chipset in x61 (see previous thread). Both memory types are compatible to your ThinkPad.

Marin85 wrote:AFAIK PC2 5300 and PC2 5400 are actually the same type, only labeled differently by different manufacturers

That is correct. ("Some manufacturers label their DDR2 modules as PC2-4300 instead of PC2-4200, PC2-5400 instead of PC2-5300, and PC2-8600 instead of PC2-8500. At least one manufacturer has reported this reflects successful testing at a higher-than standard data rate, whilst others simply use the alternate rounding as the name, as described above.")

sportfreak can put PC2 5300/5400, 6400 or 8500/8600 in his X61. There will be no difference -- apart from cost.

I have to admit I didn´t know there are 200-pin 8500 modules...

Also some vendors don't advertise the PC2 spec at all, instead referring to the three mentioned speeds as DDR2-667, DDR2-800, and DDR2-1067 (or-1066).

jdrou wrote:Also some vendors don't advertise the PC2 spec at all, instead referring to the three mentioned speeds as DDR2-667, DDR2-800, and DDR2-1067 (or-1066).

I would rather refer to these as alternative names because of 1:1 correspondences

If as Marin85 says, the PC2-6400 speed will downclock in your chipset, then there's no apparent reason to go with anything other than PC2-5300.

Does anyone know the average lifespan of PC2-5300? Does it have a huge variance from one manufacturer or model to the other?

Welcome to the forum!

I´m not aware of any life span variances across the well-known manufacturers. It´s rather the question whether some module is not faulty and whether it´s compatible with the machine in question. In the early era of laptop CoreDuo and Core2Duo there were some memory modules from Kingston with supposedly right specs, but incompatible with some ThinkPads based on those chipsets. I believe this has been resolved since then.

Is there a particular reason why you are interested in system memory life span? I guess, nowadays there is higher chance that some other laptop component (like screen, gpu, power jack etc) dies before this happens to a RAM module (again provided no fabrication defects/faulty modules).

Cheers,

Marin

Most semiconductor devices that fail do so shortly after first being put into service and are covered by the manufacturer's warranty. If a RAM module doesn't fail within 30 or 60 days it's unlikely ever to fail during the life of the system in which it's installed. But even so, considering that 2GB modules currently sell for ~$20, their expected life is a minor issue. Hard disks have much higher failure rates and are far more expensive to replace, especially if you don't have current back-up.