First, Intel specs state that these mobile processors support 16GB of memory: i7-2920XM, i7-2820QM, i7-2720QM, i7-2717QE, i7-2655LE, i7-2610UE, i5-2515E, i5-2510E.
Check the specs by clicking on each processor on these pages:
Regarding the 3 x 4GB memory configuration, that does not seem to make sense, since all these processors are dual channel memory devices. That would mean one channel has slots for two SODIMMs?
Next, as touched on just above, you will be at the mercy of the laptop manufacture regarding how many slots are available for memory, and if you could find compatible 8GB SODIMMs if only two slots are available, and if the BIOS and mother board support that much memory. That would concern me as much as whether or not the CPU will support that much memory. Meaning, the CPU can, but will the rest of the laptop support or allow it?
I can't comment on the discrepancies between the documents, I don't know which is correct.
Max Memory Size (dependent on memory type)
You're welcome... actually, I hope that helped you. I posted this link previously, but I feel it will be important, so for convenience, here it is:
The following is from that document, section 2.1. There is a table in the document under this text that will be useful too:
The Integrated Memory Controller (IMC) supports DDR3 protocols with two
independent, 64-bit wide channels each accessing one DIMM. It supports a maximum
of one unbuffered non-ECC DDR3 DIMM per-channel; thus, allowing up to two device
• DDR3 Data Transfer Rates
— 1066 MT/s (PC3-8500), 1333 MT/s (PC3-10600), 1600 MT/s (PC-12800)
• DDR3 SO-DIMM Modules
— Raw Card A – Dual Ranked x16 unbuffered non-ECC
— Raw Card B – Single Ranked x8 unbuffered non-ECC
— Raw Card C – Single Ranked x16 unbuffered non-ECC
— Raw Card F – Dual Ranked x8 (planar) unbuffered non-ECC
• DDR3 DRAM Device Technology
Standard 1-Gb, 2-Gb, and 4-Gb technologies and addressing are supported for x16 and
x8 devices. There is no support for memory modules with different technologies or
capacities on opposite sides of the same memory module. If one side of a memory
module is populated, the other side is either identical or empty.
Ranks or ranked refers to the mounting of the memory chips on the printed circuit card. Each side of the card is a rank, so dual ranked means chips on both sides of the card, just to be clear. It might sound like two "devices" can be used per channel, as in cards, but that statement refers to ranks, not cards.
While I am not a laptop expert, if what is underlined is true, it clearly states "one... DDR3 DIMM per-channel". That would be a major mistake if two DIMMs could be used per channel. Since this is a dual channel memory controller, there would be two DIMM slots total. This contradicts what Dell apparently told you about four slots, unless that are confusing that with ranks.
Next, according to Table 2.1, 8GB DIMMs (of the correct type) can be used, so with two channels, you have 16GB. So, why do most of the i5 and about half of the i7 mobile CPUs, and the one you are referring to have specs of 8GB max? I don't know. I sure can't tell you what is right.
Did you look at other laptop manufactures? I looked as some ASUS notebooks (what a pain, you can't tell what series has what features with their descriptions.) Here's one that claims to support 16GB and use four DIMMs!! (Click on Specs):
So I can see your problem and confusion clearly myself. Frankly, I don't know what to tell you. I can't imagine ASUS would lie in print about the memory capabilities. Does Dell not have this info on their web site? Do they consider all laptop users to be non-enthusiasts or PC illiterate? Good Luck!!
I do know that in the Desktop PC world, the specs for certain things like a CPU's supported memory speed are completely ignored by many mother board manufactures, and they spec their boards to work with memory at twice the speed of the Intel spec, and they work fine. Memory manufactures do this as well, providing the "out of spec" memory, which I am using right now, works perfectly. So are two DIMM slots per channel used, contrary to the document? Apparently, but why I really don't know.
Many thanks for a very comprehensive response, parsec. Muchly appreciated.
On the one hand, I am slightly heartened that it does not just appear to be a case of me misinterpreting specs.
On the other hand, I am somewhat frustrated that it is not easy to find a definitive answer.
Your answer is probably the most comprehensive one I will get, yet I will leave the question open for a bit just to see if anyone else can contribute.
Incidentally, regarding http://www.intel.com/Assets/PDF/datasheet/324692.pdf , section 1.2.1 of it says:
"Using 4Gb device technologies, the largest memory capacity possible is 16 GB,
assuming dual-channel mode with two x8, dual-ranked, un-buffered, non-ECC,
SO-DIMM memory configuration."
Which contradicts the individual processor specific specs. for the processors in which I am interested (see my previous point).
And finally, I note that the Asus specs. (at http://usa.asus.com/Notebooks/Gaming_Powerhouse/G74SX/#specifications) say that 16 GB is possible for a Quad Core whereas only 8 GB is possible for a dual core. I believe the i5's are dual core and most/all(?) of the i7's are quad core?
I guess I will sadly either have to bite the bullet and get an 8 GB laptop, or wait another year or so until 16 GB becomes either fashionable or possible in [top-end?] "ordinary" laptops.
Many thanks again.
Thanks for your kind words. I thought I'd check the i5 - dual core - 8GB memory idea, and it seemed to be correct, until I checked the i5-2515E mobile CPU, which has two cores (and four threads, as they all do) but then is the first i5 that spec's 16GB of memory! I imagine that the extensive array of mobile CPUs that Intel has (seems to be more than desktop models) becomes somewhat confusing regarding specs, but if you can't get the correct specs from Intel, where can you get them?
I checked the specifications update document for the i5 and i7 mobile processors, and there was nothing about supported memory amount. Among the i5 mobile processors, the 'E' suffix CPUs (i5-2510E) are spec'd for 16GB of memory.
I looked at the Alienware (actually Dell) web site, their laptops use mostly i7 mobile CPUs, and in some of their specs they clearly state that 4 DIMMS are used for 8 or 16GB of memory. But... they have one model that can have 32GB of memory, from their factory. Click on the Tech Specs tab:
Yep, it's all clear to me now... not.
If I may ask, do you really need 16GB of memory? You've heard that before, right? Apparently you know you do, but just wondering.
You are welcome Eamonn, glad I could help you, but are you sure I am? I can't imagine that Dell would be misrepresenting the reality of the memory capacity of those PC's, particularly in their Alienware line of enthusiast oriented laptops, whose owners would more likely be professionals or enthusiasts that know the details of PCs. Those users would really rip Dell if that was false, and their credibility would suffer along with market share. I have no doubt that Alienware laptops configured with 32GB of memory would be rather pricey, to put it mildly.
But now what has got me wondering is, I can't find any single 8GB SO-DIMMs. That would be at three of the major US e-tailers, none of them have them. So even after we think we found laptops with four DIMM slots, you can't have 32GB total without 8GB modules. I checked G.SKILL, Corsair, Patriot, and Kingston, and none of them have single 8GB DIMMs. I'm not a laptop user, so I just might not understand how it works with them, but either I'm missing something very basic, or maybe they are lying!
Ahh, you're a professional, so you actually will use more than 4GB. Actually, on a desktop with Win 7 64 bit Home Premium, with Firefox running and not much else, I'm using about 1.8GB of memory. That does not include any video allocated memory. I'm not an expert in this area, but given that some people get by with 2 - 4 GB, that doesn't seem very easy on the RAM. I do use large jpg files for the desktop background, up to 500MB, if that matters.
If you don't use one now, may I suggest a SSD? I know, not cheap, and you would need a HDD for general storage, but IMO a SSD is the best performance upgrade you can get, if you have a good CPU. Also, a SATA 3Gb/s interface is important and is just fine for a SSD. Best of luck!
Ok, parsec, and thanks again for your responses.
You may not believe how refreshing it is to get responses that - whilst it may take a little time to digest the technical information in them - they are galaxies ahead of the [pathetic, in my opinion] responses I got from Dell.
Once again, many, many thanks.
All the best.
Apologies for being so late to the party. I've just recently started looking for a laptop myself, very similar to your basic requirements. I'd be surprised if you hadn't already made a decision, but in any case, I was able to find a little bit more information.
Now that there are 8GB modules in the wild, it seems the mobile i5 pages on ARK have been updated to reflect that they're capable of handling 16GB.
There are a couple mobile i7's (the 2630QM and 2670QM, to be precise) which still state that they're only capable of handling 16GB, rather than the 32GB that the other mobile i7's state.
However, on another forum, someone tested 32GB with the 2630QM, and it recognized it, without running in single channel mode, even.
One caveat to all of this is that Microsoft has artificially limited versions of 7 less than Professional to 16GB.
It would appear that the chips themselves are not so much limited in RAM addressing capacity as they are limited in DIMM bank addressing capacity; that is, for whatever reason, the dual-cores are only capable of addressing two slots worth, while the quad-cores can address all four slots. I suspect, but cannot prove, that the specifications listed as maximums addressable were simply using those limits with the maximum known module size at the time.
(See discussion on Thinkpad W510 and W520; dual-core models only have 2 DIMM slots while most but not all quad-core models have 4 DIMM slots. I can't seem to find the disclaimer on Lenovo's site where they state that even if you physically have 4 DIMM slots the dual-cores can only see two of them.)
That would give us 8GB for a dual-core at the time you did your research, but 16GB now, and perhaps 32GB at some point in the future, with doubled numbers for the quad cores, of course. As for why the E's seem to have been different, that's anyone's guess-they don't appear to differ from their brethren now.
Provided that the slots are physically present as well as electrically conductive, it does come down to the CPU & OS, so you don't need to check every motherboard model from every manufacturer, so long as it establishes that all four slots are usable.