Can anybody tell me in what order to add memory in the 4 slots (2 under KB and 2 under bottom cover)

for best performance? I ordered just 8GB from Lenovo and now what to add. The supplied 8GB seems to be installed

under the KB.

Thanks

The two slots under the keyboard are #3 and #1. The two slots on the underside of the laptop are #4 and #2.

They need to be populated in pairs using matched identical timing memory pieces, in order to run optimally as "dual channel". If only a single stick is inserted then you get non-optimal "single channel" mode.

The slots below the keyboard are harder to get to, since the keyboard must be removed first.  And the two slots are one-over-the-other (i.e. one lays on top of the other), so it's a bit tricky to handle things.  The underside bays are flat and easy to get to.

If you don't want to be bothered with the "hard to get to slots", your best advice is to order TWO memory sticks from Lenovo with the machine, and they will then be factory installed in the two under-the-keyboard slots #3 and #1.  That leaves the other two easy to access underside slots #2 and #4 for you to add additional memory to at some later date.

so the order does not matter? can I have one stick under keyboard and another in the easy to access slots.

Also not clear if configurator gives the option of two 8 GB sticks .. you get a 1x8GB or 1x16GB.

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so the order does not matter? can I have one stick under keyboard and another in the easy to access slots.

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The order DOES matter.  The "pairs" are important, if you want superior "dual channel" memory operation.  Otherwise, if you don't populate the "paired" memory slots with matched pairs of memory sticks, you will get inferior "single channel" memory operation. The machine will still work, but you won't be operating optimally.

So, for best performance you have to use both under-the-keyboard slots (#1 and #3), or both easy-to-access underside slots (#2 and #4).  Or all four. If instead you use one memory stick in each of these two "pairs" (e.g. one under the keyboard from Lenovo and one underside from yourself because it's easy to get to) rather than populating both slots of one "pair" before using the other pair, you will get "single channel" result.

So if you buy one memory stick from Lenovo, they install it in #3 under the keyboard.  If you want to add your own second memory stick you should install it in the second under-the-keyboard slot, #1.  Hard to get to because you have to remove the keyboard to install it yourself, but that's where it should go for best results.  Yes, you can in fact install it in either of the easy slots (#2 and #4) and the machine will in fact work, but that's not the optimal "paired" location #1 to go along with the single Lenovo stick in #3 under the keyboard, so you'll get "single channel" behavior.

Make it easy on yourself. Buy two sticks from Lenovo, and let them do the hard job of using the under-the-keyboard installs for the two sticks in #1 and #3, and get optimal "dual channel" performance.  Then you can use the two easy to get to underside slots #2 and #4 later if you want to add an additional two sticks yourself.

Just to add, the under-keyboard installation is not really very difficult to do yourself. I did it the day after I got my P50 because Lenovo, like all OEMs, charges way too much for RAM. Also, I wanted ECC RAM, which is the main reason to opt for the Xeon processor that Lenovo offers on the P50. (Performance-wise it's barely better than the top i7; it just supports ECC.)

There are YouTube videos to help you, but you basically just need to remove the bottom panel, which allows you to remove the keyboard screws, then you slide the keyboard up and flip it over, then remove the RAM cover. It actually only takes maybe 10 minutes. The hardest part I experienced was getting the RAM to snap in, which actually took me about another 10 minutes. But that would have happened installing either on the top or the bottom; it's just a little tricky figuring out whether the RAM is actually "in" or not before trying to snap it in place.

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Just to add, the under-keyboard installation is not really very difficult to do yourself. I did it the day after I got my P50 because Lenovo, like all OEMs, charges way too much for RAM.

 

There are YouTube videos to help you, but you basically just need to remove the bottom panel, which allows you to remove the keyboard screws, then you slide the keyboard up and flip it over, then remove the RAM cover. It actually only takes maybe 10 minutes.

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I agree, regarding the over-pricing of memory from Lenovo.  I made the same decision for my P70 and bought my second 8GB from Crucial (first 8GB from Lenovo with the P70) thinking it would be just like every other machine I've ever added memory to.  But I had never needed to get to an under-the-keyboard location before, so I was a rookie here.

The HMM wasn't really that clear with its wordless diagrams with schematic arrows drawn to try and imply what you're supposed to do, but while you can say "then you slide the keyboard up and flip it over" that actually is quite an inscrutable task if you've never done it before.  I had no idea how to slide the keyboard a bit out from its current installed and seemingly quite solid and secure position so that I could actually lift it up and over.  There are no finger-holes or other plastic protrusions for you to grab onto, so I ended up using a small screwdriver and inserted it into a tiny opening and then rotated it, to pry the keyboard loose and get it moving. I know this surely isn't what you're supposed to do, but I just couldn't figure out any other way to make it happen.

In the end, I of course did have success. But in the end I only saved $40 on the cost of Crucial 8GB vs. what Lenovo wanted for the same 8GB.  Had I known about the keyboard surgery required at the time I probably would have just paid the difference and saved all the time I invested myself (which surely also has some cost).

Of course if I were dealing with one or more larger non-ECC memory sticks, or even worse ECC memory, I'm sure I would be thinking differently as the price differential between Lenovo and Crucial is much larger.  And of course now that I've actually removed and reinserted the keyboard once, I'm now "an expert".  So it wouldn't be so daunting if I had to do it again.  Would probably take the 10 minutes you say is really all you need, if you actually know what you're doing.

Please suggest me which RAM is best for this machine, I mean Clock speed, Bus speed, ECC or Non ECC..What kind of RAM is best  or Good. 

I disagree with the posts about which slots to fill.  I believe that on newer chipsets, the system figures out which slots are populated and configures accordingly.  The only exception is 4-slot machines with 2-core mobile processors.  Only 2 of the 4 slots work.  If I remember correctly, my statement applies to Ivy Bridge and later machines.

If you bought the machine with ECC memory, you should add ECC memory.  If you bought it without ECC, you should add non-ECC. 

@richK

The P50/P70 system will configure itself regardless of the memory slot order, but will not enable dual-channel mode unless the slots are filled in the correct order. So Slot#1 and Slot#3 (under the keyboard first), then Slot #2 and Slot #4 under the back cover.