What are the pro's/con's of 4/8/16 GB RAM Sticks?

[chriscambridge]

Members,

I have a question on RAM that I am hoping to get some advice on..

What are the pro's/con's of 4/8/16 GB RAM Sticks?

I don't obviously mean what are the benefits of having more memory, but rather larger memory sticks, totally to the same amount as smaller sticks.

For instance, is there a benefit over n*8GB sticks, rather than 2*n*4GB sticks e.g. 6*8GB rather than 12*4GB?

I hope that makes sense!

Chris

[nick]

thats a weighted question there are many situations why 1 2 or 3 sticks may be better what cpu are you using? then there is ram speed latency and a few other things

[chriscambridge]

Hi Nick,

The processors are 2x E5-2670 Xeon's v1.

The motherboard is LGA 2011 and uses quad channel memory, and has 16 memory slots.

The memory I am considering using is SAMSUNG 4GB PC3-10600R 1333MHz 2Rx4 Reg ECC RAM.

I was thinking of using 16 sticks (64 GB) so that each motherboard memory slot is full.

Thanks,

Chris

[UBT - Timbo]

Hi Chris

Check out this review:

http://www.pcworld.com/article/2982965/ ... mance.html

So, in short, 4x smaller sticks will outperform (in bandwidth terms) 2x larger sticks (to give the same memory capacity), IF the CPU and mobo are both quad channel capable. But in all other tasks, there's little or no performance difference.

However: This are some other things to consider:

Larger memory sticks cost more than smaller capacity sticks
Memory prices start high (when they are introduced due to lack of supply), then drop low, when production reaches saturation and then goes high again, once production ceases and a new type of memory comes out.

So, with that in mind, 4 smaller sticks might be slightly cheaper than 2 larger sticks, BUT eventually the larger sticks will reduce in price and then is a good time to get more memory. But if you have already got 4 smaller sticks, you'll have to sell them all and buy 4 of the larger sticks.

Whereas if you just bought 2 of the larger sticks for now, when prices drop you can double your memory cheaply and you'll have 2 free slots to put them in.

And with more memory, so you can then run some more VM's and earn more BOINC credits !!

Just my 2 cents.

regards
Tim

[chriscambridge]

Hi Tim,

I read that post.. See my next post to see if my understanding is correct.

Would you say 64 MB of RAM is a large amount of memory for this type of setup (16 cores / 32 threads)?

In terms of VM's I have a very small understanding from Java, and setting up Linux on Google Cloud, but not much. I had noticed that some users where running VM's and they were showing as separate 'machines', but I assumed these were E7 Xeons (etc) basically CPUs with huge number of cores.

Surely if you run 2 VMs on a machine, you will only have 1/2 the CPU and GPU processing that you would have if you were only running one instance?

I bought the Xeon E5-2670 SR0KX version which is C2 stepping, rather than the SR0H8 version which has C1 stepping - which has a bug that doesn't allow for virtualization!

Chris

[chriscambridge]

I have been doing some research and it is now my understanding that because the RAM above says PC3 and runs at 1333 Mhz then this means its DDR3.

Additionally I now understand that the difference between DDR3 and DDR4 is the speed the RAM runs at, rather than quad or triple channel.

So if my mother board says it uses quad channel memory, then this just means that I have to fill the first 4 slots (as specified by Intel) for each CPU. Which if I fill all slots does not obviously make any difference.

Am I correct in this understanding?

However, I am still not really clear of the pros and cons of 8 x 8Gb over 16 x 4Gb sticks? (on a quad channel, 2 CPU MB)?

(Motherboard Supported Memory Types DDR3 800/1066/1333/1600)

Am I right in thinking that all 240 pin RAM DIMMS are the same size and will fit any RAM Slots on motherboards that use 240 pins.

And lastly, how can I find out the number DIMM RAM pins this motherboard slots use?

Chris

[UBT - Timbo]

Hi Tim,

I read that post.. See my next post to see if my understanding is correct.

Would you say 64 MB of RAM is a large amount of memory for this type of setup (16 cores / 32 threads)?

Hi Chris

I think you mean 64 GB !!

And yes, that should be large enough for most things.

In terms of VM's I have a very small understanding from Java, and setting up Linux on Google Cloud, but not much. I had noticed that some users where running VM's and they were showing as separate 'machines', but I assumed these were E7 Xeons (etc) basically CPUs with huge number of cores.

Surely if you run 2 VMs on a machine, you will only have 1/2 the CPU and GPU processing that you would have if you were only running one instance?

I bought the Xeon E5-2670 SR0KX version which is C2 stepping, rather than the SR0H8 version which has C1 stepping - which has a bug that doesn't allow for virtualization!

Chris

A VM does use up some of the CPU "processing power"...but the idea behind a VM (as far as BOINC goes) is that you can run multiple instances of the NCI type tasks and the CPU has enough power to allow this without taking too much away from using the CPU for other more demanding tasks.

Obviously, it's a question of balance and so you should be able to experiment once the rig is working and see what works best for you.

As far as the GPU's though, those would not generally be run via a VM as the tasks are (generally) data intensive and the VM would get in the way (so to speak).

Yup - the C2 is the one to go for !!

regards
Tim

[UBT - Timbo]

I have been doing some research and it is now my understanding that because the RAM above says PC3 and runs at 1333 Mhz then this means its DDR3.

Additionally I now understand that the difference between DDR3 and DDR4 is the speed the RAM runs at, rather than quad or triple channel.

Hi Chris

The architecture of the RAM modules varies from mobo and CPU design, every couple of years. And sometimes mobo's can support two different types - the "current" one and the one that will replace it the next "model year".

So if my mother board says it uses quad channel memory, then this just means that I have to fill the first 4 slots (as specified by Intel) for each CPU. Which if I fill all slots does not obviously make any difference.

Am I correct in this understanding?

That's correct, as far as I know.

However, I am still not really clear of the pros and cons of 8 x 8Gb over 16 x 4Gb sticks? (on a quad channel, 2 CPU MB)?

(Motherboard Supported Memory Types DDR3 800/1066/1333/1600)

Am I right in thinking that all 240 pin RAM DIMMS are the same size and will fit any RAM Slots on motherboards that use 240 pins.

And lastly, how can I find out the number DIMM RAM pins this motherboard slots use?

Chris

Not all 240 pin DIMMS are the same - for instance there are non-ECC and ECC (aka registered) types of memory. Likewise, I think some 240 pin DIMMS have a locating slot in a different place, so as to prevent the wrong memory modules being used.

So, the safe bet is to either go to one of the memory modules firms (like Crucial) and use their website to see which modules suit your mobo. Or check the mobo manual and see what they suggest.

Then get the fastest speed of RAM you can afford. Obv 800 is slower than 1066 and 1600 is the fastest. But there's a premium to pay for the "fastest". So, you pays your money...

regards
Tim

[chriscambridge]

Thanks Tim,

I did check Crucial but it seemed to be saying the same DDR3 240pin ECC R ram that I already have in my other dual Xeon machines.

Is there some kind of identifier that differentiates between the different types of 240pin DDR3 ECC R ram sticks, apart from the notch?

I think it may be different as an Ebay seller was saying these do not fit Intel motherboards.

Chris

[chriscambridge]

I just checked the MB specification..

http://ark.intel.com/products/66133/Int ... -S2600CP2J

And it says:

"DDR3 ECC UDIMM/LV RDIMM/LV 1066/1333/1600/1866, Load Reduced 1333/1333LV".

I guess LV stands for low voltage which could explain why the RAM above won't work. Its Registered, which I guess is the same as RDIMM.

--

Additional information..

http://www.intel.com/content/www/us/en/ ... 600cp.html

--

I also just checked the interactive layout tool which shows what the different parts of the MB are, and it says '240 pin DDR3 SDRAM DIMM'.

https://www-ssl.intel.com/content/dam/s ... layout.swf

I must say I am very impressed with the above flash tool, very useful for newbie builders.

--

So I think I have to find 'DDR3 EEC LV RDIMM 1066/1333/1600/1866 240 pin'.

Or, 'DDR3 EEC UDIMM 1066/1333/1600/1866 240 pin'.

[chriscambridge]

I am right in thinking that PC3L is the same as DDR3 LV?

http://www.ebay.co.uk/itm/Hynix-8x8GB-6 ... SwNRdX--uT

[Woodles]

The processor fetches code and data from memory and writes the new data back. Fetching code is usually an easy task as the instructions are sequential and the memory controller fetches a series of consecutive locations each fetch. Data is different in that it can be anywhere in memory. RAM is fast but not instantaneous, for a read, the processor puts the address on the bus and waits for the data to come back. For a write, the data is also held on the bus. During both these times the bus can't be used for anything else. With two channels, a second memory access can be started while waiting for the first to complete.

In the old single core days, a single memory channel was enough as the processor was waiting anyway so a second memory cycle wasn't much use (very simplified case) With multiple cores, it's more likely that another core would also need a memory access but would have to wait for the first core to release the bus.

Multiple channels allow multiple accesses to occur at the same time.

The best set up is to put RAM in all the channels that the processor AND the board support. Since your motherboard supports 4 per processor and the processor supports 4, you want a multiple of four RAM modules per processor (eight for two processors)

While Tim is correct about memory price patterns, DDR3 memory is pretty much an established standard these days and in my experience, one 8GB module is usually just less than two 4GB modules. I'd echo his recommendations of getting the bigger capacity sticks to start with.

I would say that 64GB is a lot of memory, you shouldn't need anywhere near that much. My dual Xeon set up has 24GB and it never gets near to using all of it (although it is only 16 threads) Most BOINC tasks use a few MBs at most so 1GB per thread would be plenty. Unless you find yourself regularly using the swap disc, eight 4GB modules should be fine. With eight 4GB modules, you can always add another 32GB later if you find you need it.

A virtual machine is allocated a maximum number of cores and an amount of memory and basically runs as a separate computer. You could set up a VM to use 1 core and 1GB if RAM and your main machine would still have 31 cores and 63GB of RAM (using your initial figures and hyperthreading turned on) If the VM isn't using the full CPU core, its still available to the main machine although the RAM can't be shared. (in the past, I've had 100+ VMs all sharing the same core while not being heavily stressed) Any GPUs can be allocated to either your main machine or the VM (but not both)

DDR4 memory is not worth considering at this point, it only gives a single digit improvement for a much higher price.

I think Tim's covered the differences between the 240 pin modules?

LV is low voltage, RDIMM is registered. You don't need either nor does it have to be EEC. I can't view the datasheet on my 'phone but "The board supports DDR3 ECC UDIMM/LV RDIMM/LV 1066/1333/1600/1866, Load Reduced 1333/1333LV" means EEC or unregistered, non corrected or registered, non corrected and regular or low voltage. Standard memory is cheaper than corrected, I don't know the differences between normal and low voltage.

And finally, in this case PC3L is the same as DDR3 LV.

Apologies for the long post and lumping everything together, but it's taken me an hour to type this on a 'phone and I'm not changing it now

[UBT - Timbo]

Apologies for the long post and lumping everything together, but it's taken me an hour to type this on a 'phone and I'm not changing it now

HI Mark

I think you should gain 100 packets of choccy Hobnobs just for persevering writing that post !!

regards
Tim

[chriscambridge]

Thanks guys its much appreciated.

My current plan is to buy the following:

4 x SAMSUNG 8GB (2x4GB) 2Rx4 PC3L-10600R DDR3 1333Mhz ECC Registered 240 PIN RAM.

http://www.ebay.co.uk/itm/351707759015

Its coming from Hong Kong but I have used this seller before to buy RAM and its okay, well packaged, and comes in useful plastic rectangular RAM containers!

Also the 32 GB (with 5% discount) is costing £45.60 with free p&p.

--

Mark, Tim mentioned different types of 240 pin RAM; the manual just says 240 pin SDRAM, as well as the info as given previously.

Do you think this RAM will be okay and fit this MB?

If so, I shall purchase it ASAP as it takes 2-4 weeks to get here.

Thanks again,

Chris.

[Woodles]

Hi Chris.

The RAM you need and the RAM you're buying is pretty much a standard for server boards, it should be compatible. It's the more unusual types that will have different codings.

Regards,

Mark

[UBT - Timbo]

Hi Chris / Mark

oops - I made a booboo - re: PC3L RAM operating voltage.

But my excuse is that it was late and my brain had been affected by going to a particularly good gig in Manchester last night hosted by Bad Company and led by the one and only Paul Rodgers....!! My, can that guy sing !!

So, my post removed in case it caused confusion !!

regards
Tim

[chriscambridge]

Hi Guys,

To be honest I did notice that, but I did not want to say anything in case I was wrong!

Thanks for both of your help, the RAM has now been ordered.

I will make another UBT donation on Friday.

Chris