First of all I'd like to introduce myself, since I'm brand new to the forums. I don't know how active I will be, but I figure I should probably say a little bit about myself. Basically, my name is Ben and I've been into PCs for a long time. In 2004 I tried an Opteron based PC and have been very pleased since then.

Anyway, I have a question about maximum RAM. There's a PC I have, currently with the following, relevant specifications:

Opteron 1354
SuperMicro H8SMI-2
8GB (4x2GB) DDR2-800 ECC Unbuffered

This motherboard has only 4 DIMM slots. According to the SuperMicro web site, they claim the maximum amount of RAM supported is 8GB. However, I wonder if this is really accurate, since a good while ago both Intel and AMD decided to integrate the RAM controller on to the CPU itself, which leads me to believe the maximum is dependent upon the CPU, NOT the motherboard.

I did find one company that produces 4GB DDR2-800 ECC Unbuffered modules. So in theory, it would be possible to purchase 16GB of RAM, and the RAM modules would physically fit. Also, the 4GB modules seem to also be dual-rank and have similar timings to what I have now.

However, would it work?

I guess the thing I'm really concerned about is if the CPU memory controller will handle the denser RAM chips. The 2GB modules I have use 18x128M, while the 4GB modules would use 18x256M.

Further complicating matters, on the Cpu-world.com page for the Opteron 1354, it claims the CPU will support 256TB of Physical Memory.

I would hate to spend the rather significant price premium for the denser modules, only to find they don't work!

I'm not yet at the point where 8GB is insufficient, but there are times when I wish I had more, and eventually more will be needed.

Whoops! I'm still trying to figure out this forum software (it's not like anything I've used in the past). So I replied to myself so I can subscribe to this thread.

That setup of four 4 GB dual-ranked unbuffered modules should work perfectly well. This is also the maximum amount of RAM you can put in the board as DDR2 does not support unbuffered modules larger than 4 GB.

The 256 TB part refers to the memory address space used by the CPU, which is 48 of the 64 possible bits. The CPU cannot physically address that much memory.

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Hi

I would be wary of running the board with more RAM than the maximum "allowed". I'm sure the CPU and chipset can accommodate larger amounts but if that were the case, surely supermicro would have said so.

You may be interested to know that I have recently moved from a Xeon server to an Opteron server. The Xeon server was an HP proliant ML150 G3 that came with 4Gb RAM. I had the good fortune to obtain some extra RAM for the server and thought it would be useful since it was used to virtualise several XP machines, so I installed 2 x 8gb + 2 of the original 1gb sticks, making 10Gb in total. Everything appeared to be working fine, the board would POST ok, the memory test would complete and windows would load. Then a funny thing happened... I was getting random lockups and blue screens in windows. Every fault pointed at the network controller, so I disabled the onboard one and installed a PCI one. This didn't solve the problem, only moved it onto something else. The strangest thing was that the machine was fine until internet explorer was loaded. It would then bluescreen and lockup. Also, some days the SQL server would simply hang and never recover (a nightmare in a production environment).

Eventually, I decided to swap the memory - i had just obtained even more RAM so was excited to upgrade... When I opened the case (for the Nth time) I finally noticed that there was an advisory "Maximum 8Gb RAM". I whipped out the 2 x 1Gb sticks and it has been fine ever since!

My advice would be to contact supermicro and ask them...

Hello friends,

I would like to say, Windows Task Manager can tell you if your machine needs more RAM. Check your PC's RAM usage by opening Windows Task Manager. Press Ctrl-Alt-Del (Vista users will have to click Start Task Manager) and click the Performance tab. If the figure next to 'Available' (or 'Free' in Vista) under 'Physical Memory' hovers around zero and your PC seems sluggish, you need more RAM.

Best regards
Rodger Hooks

^ That is correct Rodger, but if the motherboard and/or CPU does not support more RAM then you cannot add more.

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The opinions expressed above do not represent those of Advanced Micro Devices or any of their affiliates.


Edited: 03/19/2012 at 11:21 PM by Canis-X