Quick question: RAM type for my T61p

[Yacek]

Thinking about expansion and upgrading RAM in my T61p (6459 CTO DC 7500)..... is it compatible with DDR2 PC6400 800MHz ? I'm running now on PC2 5300 667 MHz.... if there is full compatibility and support, will I notice any improvement ?

[ninjaronin18]

Thinking about expansion and upgrading RAM in my T61p (6459 CTO DC 7500)..... is it compatible with DDR2 PC6400 800MHz ? I'm running now on PC2 5300 667 MHz.... if there is full compatibility and support, will I notice any improvement ?

Yeah, it's compatible with DDR2 PC2 6400. Note however the CAS Latency. Usually the CL for PC2 6400 is 6 which is worse than the CL 5 for the PC2 5300. Also, I saw on Newegg an OCZ 2 x 2 GB PC2 6400 with CL of 5. Theoretically, this is suppose to be better. In practice, I have no idea. However, there are other things that the specifications don't point out like power consumption. If I were you I would buy memory from Crucial and stick with the PC2 5300. I read somewhere that some memory brands use older types of voltages. What exactly that means I can't tell you. So the bottom line answer is that you may or may not notice any improvement depending on what you actually use your system for. For 90% of us, we won't notice the difference between them.

My stock memory went bad this past week so I ordered from Newegg and got 2 x2 GB of Crucial PC2 5300 for USD 50.00 + USD 7 for UPS 3 day shipping. If you don't need the memory at the moment, I would wait until you can find a valid promo code for Crucial memory from Newegg.

[Yacek]

Yeah, it's compatible with DDR2 PC2 6400. Note however the CAS Latency. Usually the CL for PC2 6400 is 6 which is worse than the CL 5 for the PC2 5300. Also, I saw on Newegg an OCZ 2 x 2 GB PC2 6400 with CL of 5. Theoretically, this is suppose to be better. In practice, I have no idea. However, there are other things that the specifications don't point out like power consumption. If I were you I would buy memory from Crucial and stick with the PC2 5300. I read somewhere that some memory brands use older types of voltages. What exactly that means I can't tell you. So the bottom line answer is that you may or may not notice any improvement depending on what you actually use your system for. For 90% of us, we won't notice the difference between them.

My stock memory went bad this past week so I ordered from Newegg and got 2 x2 GB of Crucial PC2 5300 for USD 50.00 + USD 7 for UPS 3 day shipping. If you don't need the memory at the moment, I would wait until you can find a valid promo code for Crucial memory from Newegg.

thanks for some thoughts. I got a chance to buy brand new 2 x 2GB Corsair pieces 6400 CL 5 800MHz for relly good price. I think Corsair is a good brand. I should note some improvement comparing to my current 2GB stock 5300 memory 667 MHz...

[msb0b]

DDR2 800 memory should work, but the T61p will only drive the memory at DDR2 667 speed. The improvements you will see is the OS getting more RAM to work with so it page faults less often and able to use that memory to cache more disk data.

Memory is a commodity. Buy it from a company with proven history of providing good and fast support. My experience with Corsair's support has been pretty good. They took 1.5 to 2 weeks to replace some bad RAM modules that I had.

Another thing is CL=6 at DDR2 800 speed is not worse than CL=5 at DDR2 667 speed.
6 cycles / 800 MHz = 7.50 ns
5 cycles / 667 MHz = 7.49 ns
Both devices will have to wait around the same 7.5 ns between most commands. However, the DDR2 800 part will be able read and write commands and data at 800 MHz, which takes less time than 667 MHz, resulting in higher bandwidth.

[ninjaronin18]

Another thing is CL=6 at DDR2 800 speed is not worse than CL=5 at DDR2 667 speed.

Thanks for the clarification. I meant just to compare CL6 vs. CL5 though. So what about PC2-6400 at 800 Mhz CL5?

[Yacek]

DDR2 800 memory should work, but the T61p will only drive the memory at DDR2 667 speed. The improvements you will see is the OS getting more RAM to work with so it page faults less often and able to use that memory to cache more disk data.

Memory is a commodity. Buy it from a company with proven history of providing good and fast support. My experience with Corsair's support has been pretty good. They took 1.5 to 2 weeks to replace some bad RAM modules that I had.

Another thing is CL=6 at DDR2 800 speed is not worse than CL=5 at DDR2 667 speed.
6 cycles / 800 MHz = 7.50 ns
5 cycles / 667 MHz = 7.49 ns
Both devices will have to wait around the same 7.5 ns between most commands. However, the DDR2 800 part will be able read and write commands and data at 800 MHz, which takes less time than 667 MHz, resulting in higher bandwidth.

these are the approximated access time for the modules (first word) - found on wiki
DDR2-667 667 MT/s  1.5 ns 333 MHz  CL5 = 15 ns
DDR2-800 800 MT/s  1.25 ns 400 MHz  CL5 = 12.5 ns

I will try 800 and will let you know the results -

[Yacek]

OK, factory memory sticks (2 x 2GB PC5300 667MHz) replaced with Corsair 2x2GB 800MHz CL5

There is a significant improvement in system load speed (about 4-5 secs). I did not make any specific software test measurements, but is it visible. And performance vista index went up from 4.7 to 5.1 and now HDD is the bottleneck with 4.9 score......