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4 x 512MB (2 x VS1GBKIT400) in a MSI K8N SLI Platinum - underclocking required?


Zakarov

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I (stupidly) bought 2 new 512MB modules of PC3200 Corsair Value Select RAM (VS1GBKIT400) to throw into my MSI K8N SLI Platinum motherboard alongside the two existing modules of the same type. It would seem that this is not allowed - for reasons I do not understand related to CPU architecture, having 4 512MB PC3200 DIMMS is unacceptable, and it seems I have to underclock my RAM.

 

I noticed problems soon after installing the RAM: random lockups would suddenly occur on games that had mere days before had run flawlessly. I've updated my BIOS but seen no improvement. I'm 99% certain the issue is with my RAM.The clincher is what CPU-Z is telling me:

 

for slot #1 and 2, it gives me the following readings: 200Mhz, 2.5-3-3-8

for slot #3 and 4, it gives me two columns of data: 133Mhz, 2.0-2-2-6 AND 2.5-3-3-8

 

and nTune gives me the following data on the 3rd and 4th modules:

 

CAS 2.0:

Cycle time (tCYC) = 7.500 ns fMax = 133.333 Mhz

Access time (tAC) = 0.750 ns fMax = 1333.333 MHz

CAS 2.5:

Cycle time (tCYC) = 5.000 ns fMax = 200.000 Mhz

Access time (tAC) = 0.650 ns fMax = 1538.462 MHz

 

while the first and second modules only have:

 

CAS 2.5:

Cycle time (tCYC) = 5.000 ns fMax = 200.000 Mhz

Access time (tAC) = 0.600 ns fMax = 1666.667 MHz

 

I'm not sure what that means exactly, but I'm pretty sure it's not good.

 

I poked around the manual and it does indeed say (I should have read more closely) that running four double-sided modules means the maximum speed is DDR333Mhz.

 

I loaded up nTune and started adjusting the "reference clock (HTT)" down until the memory bus frequency was more or less 333Mhz... and this meant my CPU core freq fell as well. Is this inevitable? Do I have to underclock my CPU simultaneously? I've got an Athlon 64 3200+, so underclocking in this way knocks me from an already somewhat lower-end 2010Mhz down to 1670Mhz

 

Have I basically just paid 100euro to make my system worse?

 

Anyway, I am hoping that underclocking to 166Mhz will work, but I'm not sure exactly how to do that properly in my BIOS: I can set it manually to 166Mhz, but there are about a dozen other options (many of which can be set to automatic, but not all) for which I have no idea about correct settings And do I have to adjust any other settings outside of the RAM to make it all work?

 

And those readings from nTune and CPU-Z seem to indicate I might have to downgrade all the way to 133Mhz - is this the case? :(

 

So, how can I do this properly and safely - sacrificing the minimum of performance without taking risks with the rest of my hardware?

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You may have 2 issues here stemming from the same act of adding new memory.

 

1. Most likely, the new memory you have is not made with the same ICs as the original memory. This is likely the source of your instability.

 

2. If the 2 sets of memory will run together then you will have to run DDR333 and the CPU at 166.

 

Try this, first test the system with only the set of memory that is registering 133mhz. See if it will run at 200mhz/DDR400 only as a pair.

 

Then, try 4 DIMMs again. Set the memory timings manually to 3,3,3,8 timings and set the memory voltage to 2.8v. Make sure the CPU is at 166mhz and the memory speed is 333.

 

If you can get stable at these settings, you "MIGHT" be able to manually clock the system back up some from 333. There is no guarantee and it will be a trial and error process to find stable settings "IF" all of modules are going to run together at all.

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You may have 2 issues here stemming from the same act of adding new memory.

 

1. Most likely, the new memory you have is not made with the same ICs as the original memory. This is likely the source of your instability.

 

2. If the 2 sets of memory will run together then you will have to run DDR333 and the CPU at 166.

 

Try this, first test the system with only the set of memory that is registering 133mhz. See if it will run at 200mhz/DDR400 only as a pair.

 

Then, try 4 DIMMs again. Set the memory timings manually to 3,3,3,8 timings and set the memory voltage to 2.8v. Make sure the CPU is at 166mhz and the memory speed is 333.

 

If you can get stable at these settings, you "MIGHT" be able to manually clock the system back up some from 333. There is no guarantee and it will be a trial and error process to find stable settings "IF" all of modules are going to run together at all.

 

1. Real issue here is that your Cpu's memory controller cant handle 4 memory DIMMs as it can handle 2 memory DIMMs. You need to run memory at DDR333 using command rate 2T. Situation would be different if you were using Opteron Cpu.

 

2. Why should he run CPU at 166Mhz? Are you kidding as? Athlon 64 3200+ should be running normally at 10x 200Mhz and in this case using divider for memory, as you mentioned, DDR333 or also known as 5/06. Then memory runs at 166Mhz=DDR333 and Cpu at 200Mhz, i cant understand why there's need for slowering down Cpu speed?

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1. Real issue here is that your Cpu's memory controller cant handle 4 memory DIMMs as it can handle 2 memory DIMMs. You need to run memory at DDR333 using command rate 2T. Situation would be different if you were using Opteron Cpu.

 

2. Why should he run CPU at 166Mhz? Are you kidding as? Athlon 64 3200+ should be running normally at 10x 200Mhz and in this case using divider for memory, as you mentioned, DDR333 or also known as 5/06. Then memory runs at 166Mhz=DDR333 and Cpu at 200Mhz, i cant understand why there's need for slowering down Cpu speed?

 

1. Opteron is not the deciding factor here. Any REV-E A64 939 CPU can handle 4 memory DIMMs as AMD improved the memory controller. 2T will likely be forced by the bios as this is a chipset requirement with 4 DIMMs. We don't know if his CPU is an older core such as Newcastle (REV-D memory controller) or the Venice or newer cores (REV-E).

 

2. Since MSI recommends 333mhz for memory with DS DIMMs it makes sense to run the CPU in synch with the memory due to the load and the combined instability. If this user had 4 identically matched DIMMs and was stable, I would not necessarily recommend slowing the CPU. However, this will aid temporarily in troubleshooting the instability problems. So, no, I'm not kidding.

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1. Opteron is not the deciding factor here. Any REV-E A64 939 CPU can handle 4 memory DIMMs as AMD improved the memory controller. 2T will likely be forced by the bios as this is a chipset requirement with 4 DIMMs. We don't know if his CPU is an older core such as Newcastle (REV-D memory controller) or the Venice or newer cores (REV-E).

 

2. Since MSI recommends 333mhz for memory with DS DIMMs it makes sense to run the CPU in synch with the memory due to the load and the combined instability. If this user had 4 identically matched DIMMs and was stable, I would not necessarily recommend slowing the CPU. However, this will aid temporarily in troubleshooting the instability problems. So, no, I'm not kidding.

 

1. Yes, can handle but not at 200Mhz/DDR400, that i meaned.

2. I see your point, but if he cant run 4 memory at 333Mhz/2T, something is wrong, usually it doesn't matter are memorys even from same manufacturer. I just dont know what you mean "due to the load", because running memory and cpu not synced but at normal or lower speed than normal isn't that much load.

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1. Yes, can handle but not at 200Mhz/DDR400, that i meaned.

2. I see your point, but if he cant run 4 memory at 333Mhz/2T, something is wrong, usually it doesn't matter are memorys even from same manufacturer. I just dont know what you mean "due to the load", because running memory and cpu not synced but at normal or lower speed than normal isn't that much load.

 

1. Yes, they can. Rev-E and newer CPUs can run 4 DIMMs at 200mhz/DDR400.

2. And yes, matching ICs is VERY important, especially in this case. When I say "due to the load" I mean the load on the chipset and the memory controller. Asynch involves more variables than synch so temporarily for troubleshooting purposes, 166/333 is best.

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Thanks for the replies guys. I've check CPU-Z and it says my revision is: DH8-D0. Guess that means I'm out of luck on the updated architecture front :[pouts:

 

As for these DIMMs being identical - they are (or at least, are as identical as any four DIMMs can be). The two pairs are the exact same model number, I made absolutely sure of that when I bought them since I'd heard it was best to avoid mixing modules of different types. Given that, would it be best to run them at 166Mhz without adjusting my CPU and see if that clears up the problem? If I do, should I use the 3,3,3,8 timings and memory voltage at 2.8v like you suggested specmike? I'm really really nervous about setting things manually since I don't want to risk borking my RAM.

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If I do, should I use the 3,3,3,8 timings and memory voltage at 2.8v like you suggested specmike? I'm really really nervous about setting things manually since I don't want to risk borking my RAM.

 

Yes, try those timings. The voltage is safe and will not damage the memory or void your warranty.

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  • 2 weeks later...

The problem here is memory rank. As you alluded to in the OP, your motherboard cannot handle 4 double-sided DIMMs. Rank is sort of like banking memory, except internal to the chip module. Hence, if your 512 MB DIMM is configured as 64Mx64, then internally there are actually 2 32Mx64 modules sharing the same CS. And because they share the same CS, the memory controller must know not to select two different 64-bit words on the 2 different (internal) modules consecutively. The tradeoff here is higher density of more common memory modules for more complexity at the memory controller level. (Tangent: Server memory modules can go up to 4 ranks, because the memory is so much cheaper that way and their memory controllers are generally more complex as a result).

 

Going back to your problem, double-sided unbuffered non-ECC DIMMs are almost always dual rank, and single sided are almost always single rank. Hence, you are trying to use 2 sets of dual-rank modules, which your motherboard can't support at DDR 400. My motherboard, incidentally, has the exact same limitation. The answer here is to either run at DDR 333, or else trade/sell your new set of memory and get a set that has single rank DIMMs. The specs will not usually tell you their rank, but you can probably assume that single sided=single rank.

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