DRAM Frequency, Timing Mode and Command Rate

Kingston 2gb pc6400 ddr2 dimm dual chann...
August 13, 2010 at 09:21:37
Specs: Windows XP
Specs...(Taken from CPU-Z)

PC2-6400 (400MHz) [800 is my max RAM speed, but my mobo can take 1066]

It says that my DRAM Frequency is at 500MHz and my FSB:RAM is 1:2 I don't know why cause I set it to 400MHz on my BIOS.

I want to get a perfect 1:1 CPU:RAM Frequency, I have my CPU clock up at 240 and my GFX at 625. I DO NOT want to touch my HT Link Speed because my computer crashed a few months ago.

-Timing Mode
There are 4 options. Auto, DCT1, DCT0 and Both. Which should I choose?

-DRAM Command Rate
Auto, 1t and 2t. Which one?


See More: DRAM Frequency, Timing Mode and Command Rate

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#1
August 13, 2010 at 13:10:48
We can't tell you if 1:1 is the "perfect" ratio for your system if you don't tell us which CPU you have, along with the make/model of your motherboard. Since you mentioned "HT link", I'm guessing that you have an AMD system? If that's the case, you can throw the whole ratio idea out the window. It applies to Intel systems, not AMD systems. And if you have an AMD system, you need to lower the HT link when you increase the CPU frequency. Don't mess with the RAM timings until you get the other issues straightened out.

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#2
August 14, 2010 at 00:19:43
I have an AMD Athlon II x2 240 CPU.

Elitegroup A780GM-A Motherboard.

[hr]

I already have the timing set (by looking at my RAM data sheet)

I left my HT Link to Auto, I don't see why 1:1 only applies to Intel, I have mine at 1:2 right now.


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#3
August 14, 2010 at 09:50:02
"I don't see why 1:1 only applies to Intel"

OK, this is going to take some explaining. The FSB (Front Side Bus) is the communication path between the CPU & the memory controller on the motherboard. The memory controller then communicates with the RAM using the memory bus. For optimal performance, both these buses should run at the same frequency. This is known as 1:1 ratio.

However, AMD stopped using the FSB many years ago when it developed the Athlon 64. The A64 & all AMD CPUs since then have the memory controller built into the CPU die & they communicate at full processor speed. By removing the memory controller from the motherboard & placing it on the CPU, they completely eliminated the FSB. Intel finally did the same thing with the "Core i" series but all CPUs prior to the Core-i (except the P4 & it's derivatives) should be run at 1:1. The P4 is an inefficient oddball & requires either 3:4 or 5:6 to perform optimally.

If you insist on a ratio, here's how it goes for your setup at default speeds:

- CPU communicates with memory controller at 2800MHz
- memory controller communicates with DDR2-800 at 400MHz
- CPU:DRAM ratio = 2800:400 = 7:1

The HT bus (HyperTransport) is the path that the CPU communicates with the motherboard. It's a product of the CPU base clock (which is always 200MHz by default) & the HT multiplier. Here's where it gets tricky. Like RAM, the HT can be reported different ways...the true speed (in MHz) or the data rate speed (true speed x 2). It can also be reported in Mega Transfers per second (MT/s). Not only that, but there have been different HT versions (HT1.0, HT2.0, HT3.0) & they all run at different speeds. To make matters worse, boards & CPUs can have different HT specs. Your CPU is rated at 4000MHz HT (2000MHz actual) but your board can support up to 5200MHz HT (2600MHz actual).

The "trick" to overclocking AMD systems is to simply run the CPU as fast as possible while keeping both the RAM & HT as close to their default speeds as possible. Increasing the CPU base clock automatically increases the HT, RAM, PCIe, PCI, etc. That means that as you increase the CPU base clock, you should lower both the RAM & HT speeds otherwise they will over-overclock & the system will become unstable. The PCIe should always be locked at 100MHz.

You raised the CPU base from 200MHz to 240MHz, correct? That means that if you haven't touched the RAM or HT settings, the RAM will run at approx 480MHz & the HT will run at 4800MHz. Since your board can support 5200MHz HT, this shouldn't be a problem. But running your DDR2-800 at 480MHz *may* become a problem. If you lower the RAM setting to 667MHz, the RAM speed will then drop to approx 373MHz & will allow you to raise the CPU base clock even higher. With the RAM at 667MHz, you *may* be able to increase the CPU base clock to 270MHz. At this speed, the RAM will run at approx 420MHz, but the HT will be at 5400MHz....that may or may not be a problem.

CPUZ is a "one size fits all" program so it has to be able to report on numerous different CPUs, therefore there have been a few compromises in the way info is reported. Just ignore the FSB:DRAM ratio...it does NOT apply to your system.


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#4
August 16, 2010 at 07:11:54
Thanks for the history information! I got the 1:1 thing from a 2005ish thread, haha. ^_^

Meanwhile, my friend fulfilled a birthday gift request asking for a new motherboard.

I now have an ASUS M4A7850-M mobo.

------------

You raised the CPU base from 200MHz to 240MHz, correct? That means that if you haven't touched the RAM or HT settings, the RAM will run at approx 480MHz & the HT will run at 4800MHz. Since your board can support 5200MHz HT, this shouldn't be a problem.

I can no longer get the 240@stock everything without crashing on the new board, the max I could get was 230.

I defaulted my RAM at 400MHz, there are only a few options IIRC, [Auto], [200],[I forgot], [400], [533] (on both the new and old board, American Megatrends). I can't see how I could get 480MHz.

As for HT link, it's set to [Auto]. I am no longer afraid to change it because ASUS loves me, LOL. One mistake with the old mobo and it's warranty time, this new one is AWESOME.

My multiplier is 14x (changeable), somehow, my new board says that I successfully unlocked 2 cores when I activated "unleashing mode", it gives me the option to activate 6 cores (I don't know why 6, Hyperthreading perhaps?) and I set the value +12% (I have no Idea what "value" did, the option ranged from -12% to +12%, 2 steps and the default was -2%).

"~But running your DDR2-800 at 480MHz *may* become a problem. If you lower the RAM setting to 667MHz, the RAM speed will then drop to approx 373MHz~"

I can't grasp this idea, how do I LOWER my RAM from 480MHz to 667MHz and get a drop? Shouldn't it be the other way 'round or something?

-------------

Note: I did this to my RAM timings, this is what the RAM's official datasheet and CPU-Z said.

CL, tRCD, tRP = CLK6
tRAS = CLK18
tRC = 24
CR = 2t (More stability, atleast from what I read)

I think these are the formulas..

Core Speed = Clock * Multiplier
Memory Frequency = Clock * Mem Freq.
HT Link Speed = Clock * HT Freq.

Although I know the formulas, I don't really understand how they relate to each other, and how low X should go for Y to increase etc.

Can you compute a theoretical maximum or, better yet, suggest how I can do it for myself?

----------------

Last, what about GFX engine clock and what software can you recommend other than CPU-Z, Cortemp, Prime95, Memtest and Rivatuner?

Not sure if this derails the topic, but I need to reinstall my catalyst to the original CD it came with (I have a Radeon HD 4650), however, catalyst fails to start-up after several clean re-installations, Ati Tray Tool says "No video board or catalyst detected" and RivaTuner does not find my Vcard with low-level O.C. like it used to, it can only do fan speed now. :(

I need to reinstall because the new 10.7 Catalyst crashed my computer, I had to use system restore + safemode, this didn't restore my old driver though. :(


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#5
August 16, 2010 at 10:02:04
Nope, you still haven't got it. There are certain settings that MUST be changed when overclocking...most importantly, RAM, HT, PCIe. If you don't make these adjustments, your system will simply lock up & you'll have to use the ClearCMOS jumper to reset the BIOS.

I just downloaded the manual for your new board so that I can look at the BIOS chapter & use the correct terminology. All these things MUST be done to properly overclock.

Under Advanced > JumperFree Config :

CPU Overclocking = manual
CPU Reference Clock = 225MHz (this is just a starting point)
GPU Overclock = manual
GPU Clock Engine = 500MHz
PCIe Overclocking = 100MHz
Processor Freq Multi = x14
HT Link Freq = 1600MHz
Memory Clock Mode = manual
Memclock Value = 333MHz

The above will run the CPU at 3.15GHz (14 x 225), the RAM at approx 350MHz (700MHz DDR) & the HT at 1800MHz.

You now have all the settings in place to overclock even higher, so all you have to do is begin increasing the CPU Reference Clock. The rest of the settings should stay exactly as listed above. If you can get the Reference Clock up to 260MHz, the CPU will run at 3.64GHz, the RAM at approx 405MHz (809MHz DDR) & the HT at 2080MHz. Notice that the RAM & HT will be running very near their deafult speeds (which is what you want), but the CPU will be overclocked by approx 30%.

NOTE: You *may* have to increase the CPU voltage to get the CPU to run stably with these clock settings.


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#6
August 16, 2010 at 10:26:26
Alright! Thanks!

Should I keep the memory timings and only change the freq?

There are still some questions left unanswered though...

~~~~~~

my new board says that I successfully unlocked 2 cores when I activated "unleashing mode", it gives me the option to activate 6 cores (I don't know why 6, Hyperthreading perhaps?) and I set the value +12% (I have no Idea what "value" did, the option ranged from -12% to +12%, 2 steps and the default was -2%.)

My GFX Engine question and Catalyst question.


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#7
August 16, 2010 at 10:59:52
"I think these are the formulas..

Core Speed = Clock * Multiplier
Memory Frequency = Clock * Mem Freq.
HT Link Speed = Clock * HT Freq"

Not exactly. Try these:

Core Speed = CPU Reference Clock x Processor Frequency Multiplier

HT Link Speed = CPU Reference Clock x (HT Link Frequency setting / 200)

Memory Frequency = Core Speed / Integer Divisor**

**The Integer Divisor is calculated by dividing the Core Speed by the product of the (actual memory setting/default memory speed x CPU Reference Clock x 2), then rounding up to the next whole number.

So using the numbers I listed in the previous response:

Core Speed = 225MHz x 14 = 3150MHz

HT Link = 225MHz x (1600/200) = 1800MHz

**Integer = 3150MHz / (333/400 x 225 x 2) = 8.4, round up to 9

Memory Frequency = 3150MHz / 9 = 350MHz


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#8
August 16, 2010 at 13:29:32
You're trying to do WAY too much at once.

Did you reinstall Windows after the motherboard change?


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#9
August 16, 2010 at 22:59:48
Do I NEED to reinstall windows o_O

I guess I need to buy another HDD soon...

Let's skip the Catalyst question for now.

~~~~~~~

I got a max of 255MHz Core Speed when I did your settings.

Good enough?

~~~~~~~

What about the core values then?

I also have a few more terminologies that need clearing-up.

Loadline Calibration

VDDNB Over Voltage

CPU/NB Frequency
- You already mentioned this, but it can only be adjusted from 2%-10% with steps of 2. I kept it on auto just to be safe.


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#10
August 18, 2010 at 11:15:10
Still there jam?

If you were offended by the "good enough?" I didn't mean it that way...I meant is 255Mhz good enough for my gaming needs? (Highest game I have is AC2).


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