Mobile Intel CPU and Memory question

Hi everyone!

I recently purchase an Acer Ethos 5951g which has 4 memory dimm slots. (two underneath and two underneath the keyboard)

I attempted to install memory into all four of the dimm slots and was met with a black screen upon restart. Removing the memory from the memory slots from underneath the keyboard fixed this.

I sent it in to Acer for repair and was promptly sent back the unit stating that because the unit has a i5 2410m processor in it, that it cannot use all four dimm slots. Only a quad core i7 model would be able to work.

Is this Acer BSing me? Or is it true that mobile i5 processors cannot address 4 dimms of memory?

 

I believe they are correct. I have read that same thing before on the forums.

 

I didn't know that...

My i3 2120 powered desktop has no problem addressing the 12gb or memory that I have (all 4 dimms populated).

Considering the architecture of the desktop i3 and the notebook i5 are essentially the same (minus the lower frequency on the notebook i5 in order to obtain better TDP) you would think it would work without issue. I don't know why Intel would change something like that.

Are the memory controllers the same?

 

Yes, you are correct.

The memory controller is likely different (guess on my part), in any case, you need a core i7 in a laptop to be able to use 4 dimms. I'm betting that your model came in both i5 and i7 flavors, they just used the same motherboard across all sub-models.

This is also the case for laptops like my M6700, only two SODIMMs can be used with the i5 variants.

 

Gyah...

Acer Canada advertises the i5 as having 4 dimms for use. It would have been nice if they would have been more specific...

Oh well, I really cant complain since I only paid 524.98 shipped to my door. :thumbsup: I'll just keep it at 8gb or the time being until I can get my hands on some cheap sandy bridge mobile silicon.

Thanks for your help guys!

 

Well, if you need more RAM, you can always go 2x8GB. It's what i'm running in my M6700 right now although it's gonna be 4x8GB in a couple of weeks.

 

Even if the memory controllers were the same, intel could have intentionally crippled the mobile dual core sandy bridge CPUs to not support more than 2 sticks of ram, maybe they want you to spend more money on a quad core CPU.

But if you really want to confirm if this really is the case, maybe email or call intel and check with them if mobile dual core sandy bridge CPUs are supposed to support more than 2 sticks.

EDIT: Didn't see posts above.

 

I wouldn't put it past Intel to voluntarily cripple the memory controller or just don't bother (because people who will use 4 SODIMMs are more likely to order their laptops with an i7 too).

If anyone knows the exact technical reason, i'd be interested to know.

 

Yeah... This is actually the first time i've ever seen a notebook with 4 dimm slots with something less than an i7 for a CPU. I honestly didn't put much consideration into whether or not it would work with an i5 CPU.

To be honest though, 8gb is more than enough for my needs at the current moment.

I WOULD however love to know the technical reasoning behind Intel's decision to alter the memory controller.

+ REP for both of you Gentlemen :thumbsup:

 

It is for most, among my circle of friends there is me and one other that actually have a need for more than 8GB, i need more for simulations, he needs more for video editing.

I do understand the feeling that you need to upgrade because you can though, i like playing with the innards of computers.

 

The manufacturers may restrict it but Intel doesn't. The memory controller restricts the total amount of RAM per channel, but it's up to the motherboard to and OEM to provide the number of slots.

 

That's strange... I mean, obviously the memory slots are recognized by the notebook since whenever I added the additional memory is when it would throw a fit. The fact that both the i7 and the i5 use the same bios just makes it more confusing. So basically what you're saying is somewhere in the bios there is an exception command for CPUs?

 

I would be surprised.

@HT, the mobile workstations come with 4 sockets regardless of the CPU and Dell, HP, Lenovo all have the disclaimer on their websites that i5s can't do 4 SODIMMs so either they're all together in some sort of conspiracy or the CPU is somehow restricting things in some way (not the number of channels, but the number of SODIMMs).

 

Well I can probably disprove that tonight, I can take the pentium B960 (dual core sandy bridge) from my toshiba and put it in my clevo (with 4 x 2gb sticks), if the notebook will not post after that then it will prove that intel is the one putting the restriction there and not the manufacturer.

If anyone really wants to see that test then I'll do it.


But the toshiba is a real pain to take apart.

 

Well it will certainly put any doubt to rest. Look forward to hearing from you!

 

If it posts then wouldn't it mean the manufacturer puts the restriction on it and not Intel? If Intel put the restriction on it then it wouldn't boot with 4 SODIMM's right? I don't know why Intel would care, they just limit the total amount of RAM available and number of channels. It's up to the manufacturer to route the memory to two channels which is what the B960 says its supports.

The Ivy Bridge CPU's say they support two memory channels yet they work with four SODIMMS.

 

Can you provide any proof for that? Because the controller is on-die, and it may very well be the CPU (cut down the IMC = save power).

It could be that it tries to map the RAM to the IMC which can't address all of them. BIOS doesn't have much to do with here, I think it's the CPU physically can't adress 4 DIMM's. Example: my mainboard in the 8560w is different than the version for a quad core CPU.
Dual core version has only 2 physical DIMM slots, while the quad core version has 4.

 

After contacting Acer, I found out that the MB is the same in both the i7 and i5 models "SM51_HR"

Looking at CPU-Z, it sees all 4 of the dimm slots.

 

Hmm, seems only quad cores support two DIMMS per channel:

Mobile 3rd Gen Intel® Core™ Processor Family: Datasheet, Vol 1

Page 13:

Spoiler

Granted in the past Intel has said certain chipsets only supported 4GB or 8GB max and users had no issue running 8GB or 16GB in the systems.

edit: here's Sandy bridge it says Sandy Bridge mobile only accepts two channels with one SODIMM per channel which is definitely not true.

http://www.intel.com/content/www/us...d-gen-core-family-mobile-vol-1-datasheet.html

Page 13:

Spoiler

 

Sorry I was meant to write that I expect the notebook to not pass post because I believe intel is the one responsibe for the restriction, but I guess I didn't proof read my post before hitting reply.
I have made an change to that post.

Anyway I'll try to do the test with the B960 today, I need to take the toshiba apart anyway to clean it and perform a contact/pressure test for IC diamond.
So I may as well put the B960 inside my clevo while I've got it apart.

 

That would be awesome. Thanks for testing! +rep...

 

Intel's specs have always been a bit all over the place, but i think it would be known by now if CPUs other than core i7s supported two SODIMMs per channel. In any case Moral Hazard will settle the question for us.

 

Yes the test will be done, but I couldn't get my girlfriend to stop using the toshiba notebook long enough to rip out the CPU yesterday, but I will definitely get it done tonight.

Sorry for the delay.

 

post picture of the GF meanwhile ... to keep the thread going

 

She wouldn't let me

Anyway I have done the test just now, the B960 would not let my notebook get past POST with 3 or 4 sticks of ram.
It turns on but the screen will just stay black, no response from the notebook, no beeps, HDD light doesn't light up at all.
No bios screen.


However as we expected it works fine with 2 sticks:
CPU-Z Validator 3.1

 

The amount of RAM in GB's isn't an issue, (an i5 has no problem running 2x8GB, and maybe it will be able to run 2x16GB once we get there), the chipset doesn't have a lot to do with it since the controller is on-die.
It's more likely that the BIOS doesn't support it.

About the second image...yeah it seems like an error to me as well, the IMC didn't change much with Ivy anyway. But you can use that info for the current discussion.
i7's most likely have 2x2 channels (2 x dual-channel) and thus can accept 4 DIMM's. The i5 could have only 1x2 channels (one dual channel) and that's the reason of only 2 DIMM support which saves on power. (this is just my guess but it seems logical)