Dual channel DDR 3 won't accept 8GB module

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VideoEditorYes

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What causes the limitation of GB OF RAM per bank preventing my preferred configuration of 2x8 GB

I have an HPE-112y elite.
MOBO= H-RS880-uATX
Dual channel requiring non-ECC DDR3 DIMMS.
MAX 16 GB currently populated by 2x4 GB ram. (8 of 16GB in use)

I do a large amount of video editing and 8 GB just doesn't seem to be able to handle the tasks as they run slowly and even slows down mouse movement as it shows the pointer in one place (while moving it) and then the pointer shows up at another location but it didn't show my pointer moving. So it couldn't even handle showing the pointer while moving the mouse.

I know there has been much debate, discussions, and answers that are not always the same regarding the optimal way to populate the banks to their max, to achieve best performance. So, I am still confused.

The MOBO specs and upgrade info at the HP site says that if I populate 3 or more banks, the speed will decrease from 1333 to 1066Mhz.
As documented at the HP site:

ISupports 1 GB, 2 GB, and 4 GB DDR3 DIMMs per socket
Supports Dual channel memory architecture
Supported speeds
PC3-10600 @ 1333 MHz*
PC3-8500 @ 1066 MHz
*DDR3-1333 modules run at 1066 MHz if three or more modules are installed.
Non-ECC memory only, unbuffered
Supports up to 16 GB on 64-bit PCs (DIMMs run at DDR3-1066)y


I have already upgraded my graphics card to ATI Radeon 5700 series and my power supply to 650 W.

Question: What is causing the 4GB max per memory bank limitation? I really wanted to put 2x8GB modules (1 in each channel) in order to access the faster speed of 1333Mhz
Were 8GB modules not available about 7 years ago or is something on the MOBO prohibiting my preferred configuration of 2x8?

Thank you!

VdeoEditorYes
 
Solution
Barty1884
The limitation (I believe) I believe is a combination of CPU and Chipset.
The CPU's memory controller can actually do up to 1866MHz OC'd, and will also accommodate the JEDEC DDR3 'standard' 1333MHz.

Even on a consumer (ie non pre-built) motherboard, those increased speeds were limited to 2 slots populated. So there's at least an aspect that's CPU related there.

The chipset will determine exactly how modules have to be populated to run. In theory, the Phenom supports 2x 8GB modules at 1866MHz (or at least 1333MHz). Sounds like HP/Foxconn limited that to 4GB modules per slot.... for some reason. There's likely quite a few possible reasons for it, a lot are above my knowledge.

Given it's 2009 release date though, 8GB...
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Barty1884

Barty1884

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The limitation (I believe) I believe is a combination of CPU and Chipset.
The CPU's memory controller can actually do up to 1866MHz OC'd, and will also accommodate the JEDEC DDR3 'standard' 1333MHz.

Even on a consumer (ie non pre-built) motherboard, those increased speeds were limited to 2 slots populated. So there's at least an aspect that's CPU related there.

The chipset will determine exactly how modules have to be populated to run. In theory, the Phenom supports 2x 8GB modules at 1866MHz (or at least 1333MHz). Sounds like HP/Foxconn limited that to 4GB modules per slot.... for some reason. There's likely quite a few possible reasons for it, a lot are above my knowledge.

Given it's 2009 release date though, 8GB was pretty substantial. 16GB was usually deemed 'overkill'..... so the fact the board is limited to 16GB across it's 4 available slots is not surprising.


Interestingly (yet no guarantee), some boards will actually support their max memory via lesser slots (so 2x8GB for 16GB total opposed to 4x4GB)..... but there's definitely no guarantee this system/motherboard is one of them.
 
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bigpinkdragon286

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Oct 3, 2012
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Primary reason for RAM limitations comes from the memory controller. In your case, the memory controller should be okay with the amount you want, within the limitations that Barty1884 pointed out, of course.

The motherboard slots where the RAM is installed can be influential in stability of RAM at given timings. All of the traces for each RAM slot are very carefully routed. Sometimes however, the slots just aren't stable with certain configurations, so the manufacturer tacks a limit on there to keep things within working parameters. There is no guarantee that the limit is in anything other than the documentation. Again, as the previous poster pointed out, we can't guarantee that your system will or won't run with the extra memory in it. The only really good reason would be due to substandard board design, or arbitrary software limiting by HP. The only way to be certain in that case is to test it and see.
 
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kanewolf

kanewolf

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Usually the limit is the number of address lines that are actually connected to the DIMM slot. If the board was DESIGNED to support a maximum of 4GB per slot then the necessary address lines to access more than that aren't connected to anything. It is a motherboard limitation.
 
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Barty1884

Barty1884

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Is/has that always been the case kanewolf? Ones I've seen have been older, admittedly - but in those cases they 'officially' supported something like 4x2GB DDR2 for a max 8GB. But populating with 2x4GB DDR2 achieved the same max config. If you then populated any additional slots, it would fail to post.

Saying that, I can;t say I've ever stress-tested them in that configuration.....so maybe that would have brought to light some issues that were not immediately obvious.
 
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VideoEditorYes

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Hi Barty, (I hope I'm posting my reply in the correct place as this was my first post ever here-so sorry if it's wrong).

Anyway, Wow! My original dilemma was 4x4GB vs. 2x8GB because I really wanted to access the 1333 MHz speed by "sticking" with only 2 modules. The max of 4 GB/slot slipped right past me when reviewing the specs. So I have searched everywhere for discussion on this 4 GB/slot limitation on a system capable of handling 16GB. I found nothing. (Until now). I can understand the limit per slot as it pertains to the maximum RAM for any MOBO but just couldn't see or find a logical reason for limiting each slot to 4GB max, when the system max is 16GB total.

Your idea that it may be a limit on the memory controller makes sense. I really don't want to attemp/risk OC'ing as it could possibly blow my CPU. (Just guessing)

Based on your comments, I will go with 4x4GB/slot. Maybe maintaining my current speed at 1066 MHz under this configuration will not even be that noticeable. Since I have had all 4 slots populated (4x2GB) since I purchased it, at least I will not be downgrading on the speed and hopefully maxing the RAM will be enough to solve my problem.

I really appreciate your response! I can finally stop searching.
Thank YOU!!!!!

Kim / VideoEditorYes
 
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