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Latency, 32-bit Win, and adding 1 vs. replacing both

Current setup:
Samsung R520 laptop
Intel Pentium T4300 @ 2.10GHz
Two memory slots: 1 empty, other has 2Gb Samsung M470T5663QZ3-CF7 PC2-6400S-666-12-E3 (CL=6)
Windows 7 Home Premium 32-bit (no plans to change OS)

1) Which options are likely to be incompatible? Which is likely to be fastest?
a. Replace CL6 sodimm with 2 so-dimms that are CL=5
b. Replace with 2 same-brand so-dimms (CL=6)
c. Add 1 so-dimm that is CL=5
d. Add 1 so-dimm (CL=6)
Assume everything matches the current so-dimm, unless stated.

2) If I try option 1.c, would it just work at the slower latency (CL=6)?

3) Since 32-bit Windows only addresses 3 Gb, wouldn't it work just as well to add a 1Gb sodimm?

4) Which is likelier to have compatibility problems:Samsung M470T5663FBC-CF7 PC2-6400S-666-12-E3, or
Crucial CT25664AC800
Both are DDR2 6400 with CL=6.

Thanks in advance.
7 answers Last reply Best Answer
More about latency adding replacing both
  1. Best answer
    you should be able to run 2 DIMMs at 5-5-5-15 without issues. When selecting RAM the timings must either be matched, or set to run at the speed of the slowest DIMM. I highly recommend replacing it with a matching pair as they are rarely sold otherwise.
  2. Thanks, Pinhedd. Anyone else have any comments?
  3. for the record you will have to add another 2GB stick otherwise you will lose your dual channel configuration (all channels must be balanced)
  4. "Crucial" to know. Thanks.
  5. Best answer selected by Rusty Shack.
  6. Here's what I did, and results:

    Bought a matching 2Gb DDR2 So-DIMM, and added it. They match, except for the product codes. (Not sure what the difference is, if any.)

    So I've got:
    Slot 1: Samsung M470T5663FBC-CF7 PC2-6400S-666-12-E3 (new one)
    Slot 2: Samsung M470T5663QZ3-CF7 PC2-6400S-666-12-E3 (old one)

    Both have 6-6-6-18 timing.

    To find the product code of my original So-DIMM, I had to pull it out and flip it over. It was in slot 2. Replaced it carefully and (I thought) fully. Win 7 came up fine, and G. Chrome worked, and didn't notice any other problems.

    It turned out that it wasn't seated properly. A week later, when starting MS Word, I got a BSoD: BAD_POOL_HEADER. :ouch: The cause was mysterious :??:, since I'd done a re-partition and a defrag in that week. However, I re-seated the old So-DIMM, installed the new one, and the BSoDs are gone. :) Since I'm using 32-bit Win7, I only see 2.96 Gb of RAM, but oh, well.

    Samsung claims their memory runs on lower power, so maybe I'll have better battery life, and since they're both Samsung and timed identically, maybe it'll run better. It was cheaper than replacing with a pair of 5-5-5-15 memory modules, uses better quality memory, and we're $20 further from starving.
  7. Good stuff. The product codes you are referring to are quite possibly the serial numbers. Each one will be unique so they will never match.

    The lower power might explain the looser timings, but that's still good if it saves money for you

    good luck
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