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Memory frequency and timing being throttled in Windows

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October 21, 2012 8:40:53 AM

I have 8GB GSkill Sniper 1600MHz 9-9-9-24 and Asus P9H77-V mobo

I've set RAM speed and timing in BIOS and rechecked it twice, but after logging to Windows, CPU-Z shows 800MHz, 11-11-11-28 (like before I changed it in BIOS)

Help please? Thanx
a b } Memory
October 21, 2012 10:11:24 AM

What does 2 X 800= ?
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October 21, 2012 10:15:25 AM

knightdog56 said:
What does 2 X 800= ?


I'm not as smart as you so I don't know
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a b } Memory
October 21, 2012 10:20:08 AM

1600 MHz
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October 21, 2012 10:25:29 AM

:sarcastic: 

OK...

So...

Where does 2 X come from, and why does 9-9-9-24 in BIOS changed to 11-11-11-28 in Windows?
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a b } Memory
October 21, 2012 10:37:35 AM

What version of windows are you using ? And what version of CPU-Z are you using?
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October 21, 2012 10:40:01 AM

I'm using Windows 7 Ultimate 64bit and CPU-Z 1.61.3 x64 (newest version on their website a few days ago)
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a b } Memory
October 21, 2012 11:01:27 AM

That is a good question, your speed is listed right but your timings are not recheck timings in BIOS.
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October 21, 2012 11:12:35 AM

You are not helping :sweat: 
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a b } Memory
October 21, 2012 11:25:05 AM

Sorry!
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October 21, 2012 11:26:50 AM

I think Asus EPU is lowering my RAM's settings to save energy. Maybe I should disable EPU all together
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a b } Memory
October 21, 2012 11:56:06 AM

Disable epu and see what happens. you can always turn it back on.
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a b } Memory
October 21, 2012 1:37:57 PM

As Stated speed is correct:
.. Bus speed is mulplied by 4 (so 4 X 100 Mhz = 400 Mhz)
.. Because this is DDR, you then multiply by 2, so 2 x 400 = 800 which is what you show.
.. Then the 3 (DDR3) means tripple channel (BUT only if triple channel if available, otherwize it will be DAUL Channel) so again multiply by 2 so 2 x 800 = 1600.

For timings. How did you change, or set in bios. If DDR2-1600 is used, that is the default for IB (default for older SB was DDR2-1333). So for IB and DDR2-1600 installed bios would auto select 1600.
However for timings it may default to a lower value (higher Numbers) than specified by Manuf,
If you look at cupz and select Memory tab for SPD You will see several settings stored on your Ram. BIOS needs to be told which one to use, or IT will decide which is default and that is NOT normally the XMP value but one of the lower JEDEC #x settings.
unless you set it in BIOS correctly, ie select XMP, then Profile 1.
NOTE if BIOS finds a problem with the Ram it MAY decrease memory performance to get it to pass Bios post check
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a b } Memory
October 22, 2012 1:27:56 AM

RetiredChief said:
As Stated speed is correct:
.. Bus speed is mulplied by 4 (so 4 X 100 Mhz = 400 Mhz)
.. Because this is DDR, you then multiply by 2, so 2 x 400 = 800 which is what you show.
.. Then the 3 (DDR3) means tripple channel (BUT only if triple channel if available, otherwize it will be DAUL Channel) so again multiply by 2 so 2 x 800 = 1600.

For timings. How did you change, or set in bios. If DDR2-1600 is used, that is the default for IB (default for older SB was DDR2-1333). So for IB and DDR2-1600 installed bios would auto select 1600.
However for timings it may default to a lower value (higher Numbers) than specified by Manuf,
If you look at cupz and select Memory tab for SPD You will see several settings stored on your Ram. BIOS needs to be told which one to use, or IT will decide which is default and that is NOT normally the XMP value but one of the lower JEDEC #x settings.
unless you set it in BIOS correctly, ie select XMP, then Profile 1.
NOTE if BIOS finds a problem with the Ram it MAY decrease memory performance to get it to pass Bios post check


I respect you, so I hate to call you out, but at least some of that is wrong.

DDR is of course Double Data Rate, so the rated speed is twice the actual bus speed. In this case, it's just 800Mhz x2 = 1600. That's really all there is to it. The DDR part of it isn't applied until you need to calculate the rated speed. It doesn't have any effect on the bus speed.

Also, the 3 in "DDR3" has nothing to do with channels. It's just the third generation of DDR. Single/Double/Triple/Quad Channel has nothing to do with the speed. More channels just allows for more available bandwidth.

DDR3-1600 is 800Mhz/1600 rated in any configuration (Single/Dual/Triple/Quad).

@OP Just enable the X.M.P. profile and all should be well.
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a b } Memory
October 22, 2012 3:14:03 AM

DJDeCiBeL, I never object to being called wrong. And respect constructive comments like yours.
While I agree that DDR3 is "It's just the third generation of DDR" it does effect the channels, Ie you can not use DDR2 for triple channel mode, But DDR3 does allow for Daul channel mode, probably the more common usage.

"The actual bus speed is obtained by a RAM multiplier (similar to the CPU)" I think that is what I stated with the 4 X 100. 100 Being the Bus speed and 4 the Frequency multiplier.

DDR, Double data rate is where the 2 x 400 comes in to play. The data is clocked on both the leading and lagging edge Vs just the leading edge for SDR. Hense effectively twice as fast as SDR.

The 2, or 3 at the end implies the Number of "sticks" that can be placed in parallel (in this case channel #s) so for two sticks, of DDR2 or DDR3, that are placed in parallel the effective speed again multiplied by 2 (or 2 X 800 = 1600). NOTE if only ONE stick of DDR2, or 3 is used you will be in single channel mode and would Lose the X2 factor.

End result is Bus speed (in this case 100) x 4 x 2 x 2.

But then I could be all wet - DJDeCiBeL Enjoy and AWAYS call be out if I'm wrong

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a b } Memory
October 22, 2012 3:30:35 AM

I edited my original reply a good bit, but everything I've ever known says that DDR just means that the bus speed is multiplied by two to get the rated speed and that it does not apply to calculating the bus speed.

And the way you say it makes it seem like a single module of DDR3 1600 RAM would only run at 800Mhz/800 rated and that Triple Channel would be 800Mhz/2400 rated. That's not true.

The amount of channels doesn't mean anything towards the speed. A DDR3 1600 module will always be 800Mhz/1600 rated, no matter how many channels there is.

All putting the RAM into Dual Channel etc. does is allow for higher theoretical bandwidth. That's why Dual Channel is only less than 5% faster than Single channel. There just isn't much advantage to super high theoretical bandwidth in most applications.

If it was the way you described it, Dual Channel should be twice as fast as Single, and so on. Even Quad Channel isn't really that much faster than single for most uses.
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a b } Memory
October 22, 2012 5:39:33 PM

SDR-400, DDR2-800/1600 and DDr3-1600/12800 ALL run at the same speed, 400 Mhz
Input Freq (MB Clock) which for SB and IB fis ixed at 100 MHz. Internally this is step up to 400 FOR all Three. Any "Speed" past the 400 is an "Effective/Equivalant" speed, not a change to the Real Frequency used.

SDR Only issuied 1 Instruction per clock pulse (on the leading edge). Along comes DDR 2 which also operats at rhe Same clock freq of 400: However; DDR 2 can issue 2 Instructions per clock pulse, one on the Leading edge (Rising)and one on the lagging edge (Falling). So for the same frequency in (400 in this case) DDR2 performs twice as many instructions, Hense it is equivalant to SDR runing at 800 Mhz. So 800 menas it is "effectively" 800 and NOT that he Memory I/O Freq is 800.

Ref: http://en.wikipedia.org/wiki/DDR3_SDRAM
Memory Clock (100) is input and I/O is internal Clock (400)

DDR2-800/1600 is simply weather the Module(s) are in single channel or daul Channel. 800 is single channel and is twice as fast as SDR 400, When two models are in parallel then again EFFECTIVE speed is doubled, ie DDR2-1600 is Effectively 4 times as fast as SDR-400. All are using the same internal clock freq of 400.

For DDR3 used in triple channel Mode (3 sticks in parallel) it is not just going from a 2 -> 2.5 Multiplier. Water is also muddied by incorrect use of equivalant freq vs MT/s

Quote (also see para in reference link after the Quote)
The main benefit of DDR3 comes from the higher bandwidth made possible by its prefetch buffer, which is 8-burst-deep. In contrast, the prefetch buffer of DDR2 is 4-burst-deep, and the prefetch buffer of DDR is 2-burst-deep.
End quote.
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a b } Memory
October 22, 2012 6:36:57 PM

That Wiki is confusing and something is being lost in translation.

On that page, if you scroll down, it says that the Memory clock for DDR3 1600 is 200Mhz (not 100) and that that gets multiplied by 4 to get 800Mhz (bus clock). No where in that does it say that DDR has any part in that. The bus clock has nothing to do with DDR.

I'll stick with what I know is right, and that's that the 1600 effective is the DDR part and has nothing to do with Dual Channel. If I'm wrong about that, then everyone here that's ever said that (and there are MANY, and many that I trust) is wrong too. I just don't believe that. There can't be THAT many misinformed people. If there is, we all need to just quit doing this because we're all obviously idiots, lol.

Edit: I think I know the part that's confusing you.
Quote:
DDR3 SDRAM gives a transfer rate of (memory clock rate) × 4 (for bus clock multiplier) × 2 (for data rate)


Since DDR3 1600 has a base of 200Mhz, that's 200x4 = 800, then 800x2 = 1600. That's exactly how it should be.

I'm just trying to figure out where you're getting that Dual channel is what makes it 1600. I've never in my life seen or read that anywhere until you said it. I'm confident enough in what I know, though, that I would bet my house/car/life savings that Dual channel has nothing to do with the effective speed.

If the channels had anything to do with that, then it's like I said above. Triple channel DDR3 1600 would be 2400 effective and Quad would would be 3200 effective. :o  I think we can agree that that's not feasible or anywhere close to accurate.

A single stick of DDR3 1600 will always be 800Mhz real/1600 effective, as will 2, 3, and 4 sticks in Dual, Triple, or Quad channel. All that changes is the theoretical bandwidth.

http://en.wikipedia.org/wiki/Multi-channel_memory_archi...
Quote:
Dual channel should not be confused with double data rate (DDR), in which data exchange happens twice per DRAM clock. The two technologies are independent of each other and many motherboards use both, by using DDR memory in a dual-channel configuration.
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a b } Memory
October 23, 2012 12:37:43 AM

KUROKO
Did you ever find out what happened when you turned off EPU?
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October 23, 2012 5:46:32 PM

Sorry for the late update :p 

BIOS recognized my RAM as 1600MHz even with EPU enabled
and after tweaking it a bit, timings were set at 9-9-9-24 with XMP.

However, CPU-Z still says that my RAM sticks are 800MHz max lol

Thanx guys :) 
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a b } Memory
October 23, 2012 5:57:28 PM

KUR0KO said:
However, CPU-Z still says that my RAM sticks are 800MHz max lol


That's actually perfect because CPU-Z only shows you the actual bus speed, not the rated, effective speed. Since 800Mhz is the real speed of DDR3 1600 RAM, you're good to go.
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October 24, 2012 7:26:29 AM

Thank you, all of you :D 
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!