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What exactly does Memory Clock Value/Limit setting do?


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#1 alokoko

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Posted 29 October 2006 - 03:07 PM

The system is in the sig (#2). Here's what I figured out so far with respect to the capabilities of the components:

CPU MAX: 2.6Ghz

HTT MAX: 260Mhz (yes, I tried to go above that but it loses stability around 270 (using x9 as CPU multiplier, so I think 260Mhz for HTT is the max for my board)

Memory MAX: 440Mhz

My initial settings were
HTT: 200Mhz
HTT Mult: x5
CPU Mult: x10
MCV/L: 400Mhz

Notes:
1- Timings manually set to 4-5-4-15
2- CPU voltage set to 1.45V (def 1.35V)
3- DIMM voltage set to 2.10V (def 1.85V)
4- HTT voltage set to 1.35V (def 1.30V)

CPU-Z reports that the memory is running at 400Mhz, 4-5-4-15-22-2T

To understand how MCV/L works, I set the system as follows (yes, I have CnQ enabled, and I would like to keep it if possible):

HTT speed: 260Mhz
HTT Mult: x4
CPU Mult: x10
MCV/L: 200Mhz

In this case, CPU-Z reports that the memory runs at 261Mhz (idle, CPU/5) and 261 Mhz (100% usage, CPU/10).

If I change the settings to

HTT speed: 260Mhz
HTT Mult: x4
CPU Mult: x10
MCV/L: 266Mhz

the memory runs at 261Mhz (idle, CPU/5) and 326 Mhz (100% usage, CPU/8). BTW, these settings are what the system is running on at the moment.

If I try to set the MCV/L to 333 or 400 Mhz in the BIOS without changing anything else, the system does not start.

I want to ask what that setting actually is. I had two ideas:

1- Judging by the wording, it should be some limit on memory speed, even though the actual speed is adjusted automatically. However, getting the memory to run at 326Mhz while this "limit" is set to 266Mhz means that this is not true.

2- If this setting implements some fixed divider (i.e. 200Mhz means 1:1, 266Mhz means 4:3 etc), I should be able to set this in the BIOS to 333 Mhz and get it working. However, it does not work as I expected. I tried the following setup:

HTT speed: 240Mhz
HTT Mult: x4
CPU Mult: x10
MCV/L: 333Mhz

Now the system boots and the memory runs at 240Mhz (idle, CPU/5) and 402 Mhz (100% usage, CPU/6).

This setup, however, is not stable. It boots but Prime95 fails in a few minutes (interestingly, when Prime95 fails and I reboot, the system DOES NOT BOOT. I have to hold the INSERT key and lower the HTT speed even more to get it working. Strange...).

I know that the CPU handles this load fine, as well as the memory (402 Mhz is nearly the stock speed). The only explanation I have at the moment is that MCV/L setting does something that I cannot figure out.

Thanks in advance for helping me with this.

#2 Spunkmeyer6

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Posted 29 October 2006 - 05:09 PM

I'd say it was your Ram, I cant get past 2.6 ghz with the 512 versions of the ones you have. Well it's the Infinity M2 I have but I could get the FSB to 290 at CPU 9x.

You could try upping the voltage to them, I had to hit them with 2.4 to get there.

#3 Booster

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Posted 29 October 2006 - 06:13 PM

I think to keep this simple for now disable CnQ so thats one less variable to worry about that would some how cause the problem. Ram voltage you can push it a bit higher from what I've read with other Platinum users are getting some really nice clocks with it. As for the memory divider confusing I hope this link will help as it really helped me when I was overclocking. http://img132.images...liers8009sg.jpg

#4 alokoko

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Posted 29 October 2006 - 08:33 PM

I'd say it was your Ram, I cant get past 2.6 ghz with the 512 versions of the ones you have. Well it's the Infinity M2 I have but I could get the FSB to 290 at CPU 9x.

You could try upping the voltage to them, I had to hit them with 2.4 to get there.


Thank you for your suggestion, I could try that. OCZ says 2.1V +/- 5% is the limit for this model, though, for warranty purposes. Even with warranty put aside, it tells me there's something wrong here, and it may not be just the RAM. I think my initial setup also supports this theory (initial setup where I had no overclock and I could get the memory to run at 400Mhz with 2.1V without any problems).

I just found out a thread in OCZ support forums that mentions about problems with their 2GB PC2-6400 kits and AM2. It does not refer to DFI specifically but I see some users not being able to run these modules to the full capacity. The thread is here: http://www.bleedined...ead.php?t=22133

In another official thread from OCZ, it is mentioned that the BIOS should have NVMM version 4.062.19. I do not know if it means anything in this case, but just wanted to point that out.

#5 alokoko

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Posted 29 October 2006 - 08:38 PM

I think to keep this simple for now disable CnQ so thats one less variable to worry about that would some how cause the problem. Ram voltage you can push it a bit higher from what I've read with other Platinum users are getting some really nice clocks with it. As for the memory divider confusing I hope this link will help as it really helped me when I was overclocking. http://img132.images...liers8009sg.jpg


Well, I think CnQ is effectively disabled when I run two instances of Prime95. :)
If need be, I will turn it off completely to see if it changes anything.

Thank you very much for the multiplier tables. Now I see that my second theory was right, and the MCV/L value in the BIOS means some fixed dividers.
(200 -> CPU/10, 266 -> CPU/8, 333 -> CPU/6, 400 -> CPU/5 for my CPU multiplier of x10).

It is interesting that the memory can run 400Mhz fine when there's no overclock, but it fails to run at the same speed in an overclocked situation.

#6 Booster

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Posted 29 October 2006 - 09:57 PM

It is interesting that the memory can run 400Mhz fine when there's no overclock, but it fails to run at the same speed in an overclocked situation.


Thats pretty weird since right now I'm running at 260x11 with a 333 limiter cpu/7 which cpuz is saying its currently at 409Mhz, I'm using the Gold version and your Platinums should have no problem with that.

Something I just noticed is that you can't get a HTT over 260 stable which I am also having this problem too.