Momory Compatility Question

[g00ey]

I've been looking around for a suitable (6GB) memory kit for an AMD (AM3 - 890 series) system and found a good deal of a Corsair 1600MHz Intel DDR3 RAM (9-9-9-24).

The first thing I wonder is will it work on an AMD system (since the description says "Intel")? I truly don't understand this.

The other thing that I wonder is since it is rated to 1600MHz will it work on a motherboard that only supports 1033 or 1333 MHz or will the underclocking lead to problems (such as Hypertransport sync flood errors)?

 

[Wolygon]

The reason why that kit is labeled "Intel" is because it is a triple channel kit. This means it has three sticks to deal with Intel X58s triple channel memory.

AMD uses dual channel, to run memory in dual channel you must install 2 or 4 sticks.

Running 3 sticks will make the RAM run in single channel mode, this does not have a "large" affect of performance but there is some. It is generally recommended to run dual channel with AMD and triple channel with X58 Intel. I would recomend getting a 4GB kit, 3GB has been shown to be enough for all "normal" uses.

Running 1600MHz RAM at 1333MHz is fine. 1600MHz is just the rated frequency which the RAM is able to reach.

Hope that helps.

 

[g00ey]

I found interesting information on the following link:

http://forums.amd.com/forum/messageview.cfm?catid=318&threadid=123894

* It basically says that a memory that is designed for Intel means that it has been tested on an Intel system but that doesn't mean that it won't work with an AMD CPU.

* The voltages is also a non-issue. Voltages for DDR3 memory ranges from slightly below 1.5V to 2.2V and all these voltages is a non-issue on an AMD system.

* There are specific posts that you can run DDR2 memory rated for e.g. 800MHz at 600MHz without problems. I don't know about the latest generations of DDR# memory but there is no indication whatsoever that you cannot underclock a memory module that is rated at a given frequency, say 1600MHz.

 

[g00ey]

Thank you for your help!

So I think I understand now; if I want to run 6GB of ram in Dual Channel mode (as it seems that triple channel is not yet supported in AMD, perhaps the Bulldozer platform does ...) I should use one 2x2GB kit plus one 2x1GB kit which makes a grand total of 4 memory modules....

 

[Wolygon]

Yeap you can run 2 2GB and 2 1 GB sticks to get 6GB of RAM. I actually wasn't aware of this and had to check. Though you most likely will not require 6GB of RAM.

The max spec for DDR3 is 1.65v, so don't buy something above this. Generally RAM is 1.5v or 1.6v.

Triple channel is not really anything special, the performance increase is like half a percent or something.

Glad I could help.

 

[g00ey]

While I agree that 6GB is probably over-the-top for most desktop applications I think it is kind of difficult to define a proper requirement for every case. I want to use extra RAM so that I have a large disk cache so as to increase disk performance and reduce frequency of disk access (which causes wear on the heads - the computer is going to continuously store a sustained stream of image data). Moreover, in a not too distant future I'm thinking of running a few virtual machines on the computer so it would be nice to spare a few extra gigs for each one of them. The motherboard also has a built in GPU so I guess that will also need some of the RAM for graphics memory (it has 128MB of SidePort memory but I'm not sure how it works). So I believe that 6GB will be a good trade-off for these applications altogether.

I read on some earlier posts that one should watch out for low-voltage memory as they were said not to work on AMD systems. After reading the thread on the AMD forums I linked to I concluded that that statement has no bearing whatsoever. While I have seen on Kingston's and Corsair's website that there are a few memory modules that operates at 2.1V I have not seen one for sale when searching on the net so I guess that these "high-voltage" modules are not much to stay away from anyway.

Thanks again.

 

[Wolygon]

You could always get only 4GB and upgrade when you see fit.

2.1v was specced for DDR2 which may be what you are talking about, though I do believe there was high voltage DDR3 which was out of spec. But I do believe these are non existent now.

Glad I could help, Good luck!

 

[g00ey]

Yes, I think you are right about the voltages. I went to Corsair's memory configurator and found memory modules for the Gigabyte GA-MA790FXT-UD5P (as they have not yet included all of the latest 890*X MoBos) which is an AM3 motherboard and is therefore only compatible with DDR3. I didn't bother to read what type of DDR they were but now that I checked more carefully I saw that they actually were DDR2:

http://www.corsair.com/configurator/product_results.aspx?id=867642

So you can't even trust the product suggestions that the vendors give you. I did some more searches but I don't remember now, I think that I found them while searching for dual-channel memory for X48 chipsets without paying attention to which type of DDR they were.

I also saw on Kingston's website that their HyperX DDR3 modules operate at 1.7-1.9V:

http://www.kingston.com/hyperx/products/khx_ddr3.asp

They claim that these voltages are for AMD chipsets and Intel chipsets older than X58 that use dual-channel memory. So it seems that some DDR2 systems can also use DDR3 memory or that the DDR3 specification wasn't completely established in the past....

 

[Wolygon]

OK I did a bit of a search on this as I didn't even know that the 1.65v limit was only for the Intel CPUs. Silly me .

So I found that there really is no physical limit on AMD boards though it is recommended to stay below 2.0v. Although "apparently" the Phenoms prefer lower voltage RAM, with stock being 1.5v.

So I would find some 1.6v or similar RAM but you are not required to stay below 1.65v.

That seems weird that they would recommend DDR2 for a DDR3 board.

I would recommend a set of Mushkins as they are very good.