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Memory bank order TWIN2x2048-6400


JBjorling

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Hi!

 

My first post on this forum. Not sure I put the post in the right department, but it was the most fitting one I could find.

 

I fixed a computer today... At least I hope I did. The problem was intermittent so it is hard to tell if the computer works probably or just haven't crashed yet.

 

My question to this forum is whether or not it makes any difference in which order you put the two RAMs in each bank. In one package of TWIN2X2048-6400 I received one CM2X1024-6400 and one CM2X1024-6400G.

 

What is the difference between CM2X1024-6400 and CM2X1024-6400G?

 

Anyway. The computer in question has a Intel Core 2 Duo processor, Nvidia 8800 PCI-Express graphics card, 4GB memory (2 packs of TWIN2x2048-6400), ASUS P5K motherboard and runs Windows Vista.

 

The problem was that when using the computer it would sometimes crash. Displaying a blue screen for about 0.5 seconds and then power-off.

 

I thought of it as a memory problem, but memtest showed no faults. So I investigated the memory banks. The ASUS P5K motherboard has two channels (A and B), each channel having two sockets (A1, A2, B1, B2).

 

I had put one CM2X1024-6400 in bank A1 and the other one in bank B2. The two CM2X1024-6400G was residing in bank A2 and B1.

 

So I swapped them, making this configuration:

A1: CM2X1024-6400

A2: CM2X1024-6400G

B1: CM2X1024-6400

B2: CM2X1024-6400G

 

And the problem seems to have disappeared.

Normally the computer would power-off after about 10 to 20 minutes of work, and now it has been running for four hours straight, so it seems as that little memory-swapping procedure did something.

 

Anyone has a clue as to why?

 

 

Thanks!

Johan

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I would suggest setting the memory Voltage to 2.0 Volts with 4 modules and with some MB's you may have to set the memory frequency at DDR667 as well.

The "G" at the end of the part # just means its RHOS compliant and both modules would be the same spec.

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Thanks. So the "G" didn't make much difference. My theory was that the memories had to reside in the same order in the banks. Although, the computer hasn't crashed yet. The only thing I did was put the memories in the order described above... I haven't changed any other setting, so it would seem that something has changed.

 

I am going to run memtest using a more extensive memory diagnostic and see if it can find any errors. I only ran a fast diagnostic yesterday.

 

My theory as of now is that when I changed the order of the memories a faulty memory switched place, so that it hasn't been adressed yet.

 

Does Vista use up memory in a sequential order or does it try to spread memory usage over all memories? If it does use memory in sequential order (first use all of bank A1, then A2, then B1 and finally B2), my theory could hold.

 

By the way... can the OS decide where to store data? I mean, can an OS choose to store data in a specific memory, or is that up to the hardware, i.e motherboard?

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Does Vista use up memory in a sequential order or does it try to spread memory usage over all memories? If it does use memory in sequential order (first use all of bank A1, then A2, then B1 and finally B2), my theory could hold.

 

A: The O.S. does not decide how to use the memory this is done by the memory controller and most MB's now use bank interleave so the information would be spread over all of the modules.

 

By the way... can the OS decide where to store data? I mean, can an OS choose to store data in a specific memory, or is that up to the hardware, i.e motherboard?

 

A: Yes and no! The O.S. can specify/request a memory address or block to be used, but exactly where the address is mapped will be done at chipset/Memory controller level.

 

Just test the modules one at a time or one set at a time if you suspect a failing module.

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