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Author Topic: Advice on RAM upgrade options for laptop  (Read 2146 times)
NigelC
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« on: November 20, 2012, 08:50:57 AM »
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I have Thinkpad W520 with i7 2720 processor and 8GB RAM (win7 64pro). The RAM is DD3 PC3 either 12800 or 10600 (not sure which) in 2 x 4GB. There are also 2 empty bays. As I'm intending to use the laptop as my desktop in future with external monitor/keynpard as my Q6600 vista 64 home premium desktop is getting abit lethargic and full back ups take about a day with acronis, I want to upgrade the RAM.

Does it matter if the bays hold an assymetric configuration? Is it faster to have fewer larger blocks?
Looking at Crucial website, to replace the two 4GB blocks with two 8GB blocks cost 58. (12800 or 10600 are same price?)
However cheaper way of achieving 16GB is to put two 4 Gb blocks in the two empty bays (18) OTOH, if i put 2 8Gb in empty bays i would have 24GB but not a symmetrical configuration.

Any thoughts? would four x 4GB be slower than 2 x 8. I got 2 x 8, should i replace existing 4s with 8s, or supplement them?

Is the answer 42, or do we have to wait for the all-encompassing universal theory? Huh

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John.Murray
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« Reply #1 on: November 20, 2012, 05:56:02 PM »
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As long as you add memory in pairs you are fine.  "Symmetry" between the alternate pairs is not an issue.  I'd double check your existing memory config and match the clock rate....
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Sareesh Sudhakaran
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« Reply #2 on: November 20, 2012, 09:31:10 PM »
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I have Thinkpad W520 with i7 2720 processor and 8GB RAM (win7 64pro). The RAM is DD3 PC3 either 12800 or 10600 (not sure which) in 2 x 4GB. There are also 2 empty bays.

First check if your motherboard will support 16 GB, if yes, what is the maximum speed it will handle. It seems like it is 1600, but it could be more.

Quote
Does it matter if the bays hold an assymetric configuration? Is it faster to have fewer larger blocks?

Yes, it does. How any motherboards out ther have three RAM slots? You need to check if your CPU can support higher than 1600.

If you're lucky, both CPU and Mobo can go higher than 1600. If yes, then get 8x2 DDR3 of whatever that speed is. If no, then find 2x2 of the same brand, same specs. If you can't, then stick to 8x2.

In real world testing, there is no difference between 4x4 and 8x2, but if you get 8x2, you have better chances of using it for the next upgrade.

Universal theory? How's this: Asymmetry in computing is a bottleneck.
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NigelC
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« Reply #3 on: November 21, 2012, 03:06:39 AM »
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Laptop spec says maximum ram 32GB (4bays)
 
Sorry, is clockrate 10600/12800/1600?

When I run the laptop through Crucial diagnostic tool it tells me RAM is 10600/12800, i.e. it doesnt tell me which. if I got a matched pair of 2 new 12800 4GB for the empty bays and it turns out existing ones are 10600, presumably only effect is that all run at 10600 effective?

If I got a new matched pair of 8GB 12800 would you replace the existin g 2x4 or leave them in (4bays available) ie. is 16GB in a symmetrical configuration faster than 24Gb in 2 diffrenet matched pairs?
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kingscurate
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« Reply #4 on: November 21, 2012, 11:08:51 AM »
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Open up your memory slot on the laptop, the ram will have what speed you have got in place. If you dont open up the laptop Of the ram you are looking at i would get the 12800(1600) as if you have the 10600(1333) in place already the new ram will  run at10600 speed. What i think you should consider more is the volt rating of the ram, i would get 1.35Volts as lower voltage = less heat, which will prevent your laptop overheating.
Leave the ram you already have in place and supplement.
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John.Murray
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« Reply #5 on: November 21, 2012, 11:20:07 AM »
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If I got a new matched pair of 8GB 12800 would you replace the existin g 2x4 or leave them in (4bays available) ie. is 16GB in a symmetrical configuration faster than 24Gb in 2 diffrenet matched pairs?

No - again symmetry between the alternate pairs makes no difference - the clock rate, however will - memory access will only be as fast as the rate of the slowest pair.  If I were faced with your choice - I'd add the additional 16GB, resulting in 24GB of RAM in a heartbeat.  The only way to determine what is currently installed is to either physically inspect it, or refer back to your original system documentation
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Sareesh Sudhakaran
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« Reply #6 on: November 21, 2012, 09:14:50 PM »
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Laptop spec says maximum ram 32GB (4bays)
 
Sorry, is clockrate 10600/12800/1600?

When I run the laptop through Crucial diagnostic tool it tells me RAM is 10600/12800, i.e. it doesnt tell me which. if I got a matched pair of 2 new 12800 4GB for the empty bays and it turns out existing ones are 10600, presumably only effect is that all run at 10600 effective?


RAM speed is four digits. 1600, 1866, 2133, etc. I would sell the older RAM on eBay, but won't use it with newer RAM, unless I got the exact same model.
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PierreVandevenne
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« Reply #7 on: November 22, 2012, 10:57:57 AM »
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RAM frequency is 1333, 1600 etc... all given in MHz

Transfer rate is 10664 MB/sec 12800 MB/sec etc...

Transfer rate in bytes is = clock x number of bits transferred / 8

Since RAM typically transfers 64 bits per access, we have TR = clock * 8

I practice, the maximun rates are higher than that because all modenr controllers support more than one channel when memorys are paired (128 data lines), added in sets of three (ex LGA 1366 platform -192 bits per transfer) or even four (ex LGA 2011 - 256 bits per transfer)

Please note that in practice, a 10% difference in RAM speed will be barely perceptible. This is because these are maximum rates, valid under the assumption that the CPU is able to request/access/execute such a transfer in each clock cycle. That's not possible in real life.
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John.Murray
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« Reply #8 on: November 22, 2012, 11:27:39 AM »
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Please note that in practice, a 10% difference in RAM speed will be barely perceptible. This is because these are maximum rates, valid under the assumption that the CPU is able to request/access/execute such a transfer in each clock cycle. That's not possible in real life.

+1

I'll have to disagree with Sareesh to a point, my experience mismatched alternate pairs has generally been good, a long as we have a good match via clockrate / access timings.  After installing be sure to run the Windows memory diagnostic (type memory in search, then select Windows Memory from the menu - the machine will reboot into the memory test).

Please understand this only applies to your socket 1155 platform.  Memory access for socket 1366/2011 is entirely different (on die controller - interleaved access), and in any case, not available in a portable computer.

I see you are contemplating Crucial?  Thats great - they will make good on any issues you may have.  Either print or save a PDF of their online scanning tool
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Sareesh Sudhakaran
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« Reply #9 on: November 22, 2012, 09:11:42 PM »
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I've had random BSOD with mismatched RAMs, but that was a long time ago. Anyway, I'm old school, and I could be wrong, but -

Let's say Nigel finds RAM that meets clock rate/access timings, who will guarantee it will work? If he can find someone who might be willing to replace it a few months down the line, would he still want to go through the hassle of being the guinea pig? For what could be a difference of about 20 bucks? I don't know.

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Steve Weldon
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« Reply #10 on: November 23, 2012, 12:38:54 AM »
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As long as you add memory in pairs you are fine.  "Symmetry" between the alternate pairs is not an issue.  I'd double check your existing memory config and match the clock rate....

+1

And one thing not oft considered.  A laptop has limited thermal capabilities and more RAM raises the amount of heat necessary to be dissipated.  With an older existing machine this increase just might be enough to exceed the margins of some existing components which have aged enough to become more heat sensitive.  Using your notebook as a desktop replacement likewise increases the amount of heat needing to be dissipated.  All blind values as far as a user is concerned, but keep the theoretical in mind when considering IF you need to add that RAM, placement of notebook in reference to other heat sources and air flow, and possible selection of cooling bases (few are worth a damn).
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NigelC
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« Reply #11 on: November 23, 2012, 03:24:21 AM »
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If I were faced with your choice - I'd add the additional 16GB, resulting in 24GB of RAM in a heartbeat. 

Which is what I've done - ordered Crucial recommended 8x2 after their system scan and will install in two vacant bays (which I suspect are under the keyboard!)
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Pete_G
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« Reply #12 on: November 25, 2012, 05:11:31 PM »
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It's always been under the keyboard in all the Thinkpads I've owned, and Lenovo make it pretty easy to get to. Best to download the service manual for your model and check any gotchas, just in case.
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