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4x2GB TWINX + ASUS P5QPRO help please


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I recently bought a new TWINX pair with same specs - see details below - to my existing TWINX pair, now I have 4x2GB of RAM.


XMS2-6400 2048MB 800Mhz 4-4-4-12 2.1V ver1.1 08180245


My existing TWINX pair only differs in the lot number: 08270703


Ran Memtest on the new modules in the yellow slot, one module at a time, both new modules and finally all four modules. No errors.


I didn't change the BIOS first, PC starts showing 8GB RAM:


However windows 7 doesn't stay stable, programs won't start. Would you please kindly help me, what should I enter into the setup to get the system stable.


motherboard: ASUS P5QPRO

CPU: Core2 Duo E8500 @3.16Ghz 3.17Ghz not overclocked


I used my existing pair with the original 4-4-4-12 settings, everything else is put on AUTO. PC worked with my original pair flawlessly.


How to set the BIOS up so the system becomes stable again with 8GB RAM?


Thank You!

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The question is: can I achieve 4-4-4-12 latency with these four modules on this motherboard? It worked with two sticks.


Found these working settings on Anandtech. Windows 7 boots, programs work. But it seems slow:


I'm currently using these very slow settings: BIOS version 2102 updated to latest.

motherboard: ASUS P5QPRO

CPU: Core2 Duo E8500 @3.16Ghz 3.17Ghz not overclocked


AI Overclock tuner: AUTO

CPU Ratio Setting: AUTO

FSB Frequency: AUTO

PCI-E Frequency: AUTO

FSB Strap to North Bridge: AUTO

DRAM Frequency: 800

DRAM CLK Skew on Channel A1: AUTO

DRAM CLK Skew on Channel A2: AUTO

DRAM CLK Skew on Channel B1: AUTO

DRAM CLK Skew on Channel B2: AUTO


1st Information:

CAS# Latency: 5

DRAM RAS# to CAS# Delay: 5

DRAM RAS# Precharge: 5

DRAM RAS# Activate to Precharge: 18

RAS# to RAS# Delay : 4

Row Refresh Cycle Time: 65

Read to Precharge Time: 4


2nd Information :

READ to WRITE Delay (S/D): 9

Write to Read Delay (S): 4

WRITE to READ Delay (D): 6

READ to READ Delay (S): 5

READ to READ Delay (D): 7

WRITE to WRITE Delay (S): 5

WRITE to WRITE Delay (D): 7


3rd Information :

WRITE to PRE Delay: 15

READ to PRE Delay: 6

PRE to PRE Delay: 2

ALL PRE to ACT Delay: 7

ALL PRE to REF Delay: 7


DRAM Static Read Control: Disabled

DRAM Read Training: Disabled

MEM. OC Charger: Enabled

AI Clock Twister: Light or Lightest

AI Transaction Booster: Manual

Common Performance Level: 12 (Tighten later)

All Pull-Ins: Disabled


CPU Voltage: AUTO

CPU GTL Voltage Reference (0/2): AUTO

CPU GTL Voltage Reference (1/3): AUTO


FSB Termination Voltage: AUTO

DRAM Voltage: 2.02 - Your board overvolts by 0.08v, so 2.02v = 2.1v

NB Voltage: 1.3 - Lower this later if you don't OC

NB GTL Reference: AUTO

SBridge Voltage: AUTO



How to make the system fast again so that it can run at 4-4-4-12?

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We need the relation between 1st Information 4-4-4-12 and 2nd-3rd Information: READ to WRITE Delay (S/D): 9 etc.. entries.


So that when I scale the latency back to 4 I must know how to decrease 2nd-3rd Information entries in concert and if there is any connection between voltages needed to be changed?


?DRAM Bandwidth? What the heck is this?

Well a product of several features, Mhz speed, 6400 MB/sec in this case as the model is named and




But explained by experts the DRAM Bandwidth is the DDR2-800Mhz and similar speeds:


Dropping the bandwidth one bin is lowering the speed of the DRAM one level. For example, 2 modules of 8500C5 run at 1066Mhz. If you add an additional two modules of 8500C5, you are advised to lower the bandwidth from 1066Mhz to 800Mhz. As per my BIOS settings.


You have passed the Memtest on all four modules? Good. Now change your BIOS settings to reflect this:


DRAM Frequency = DDR2-800


And install all four modules. Run Memtest and post the CPU-z again.





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The motherboard memory controller (MCH/Northbrige) can not keep up with the extra DRAM at the rated 8500MHz speed when populating 4 banks. This is a limitation of the chipset and follows both Intel and Nvidia chipsets.


What the hell: Manual says ASUS P5QPRO supports 16GB of RAM. No way it is driven to its knees by 8GB of RAM ??!


As it happens with the above settings I made a stress test and the PC is rock stable. Albeit slow, hence my plan to spur this horse, but not harm it. I have a big water cooling system with three big fans on the radiators blowing air onto the RAMs and the HDD.


You will need to drop the speed of the DRAM from 1066Mhz to 800Mhz. If you had purchased 4 X 1024MB of PC6400 (800Mhz) DRAM, then you would have had to drop to PC5300 (667MHz) DRAM, etc. 2 X 2048 will not issue this problem. This is a problem of all 4 banks being populated.


Think of it this way. If you have a small phone book, then when you go into the index to find the page where you will find the phone number you are doing so at a certain speed due to the pages of the Index. Then you have to drive through the pages to get to the number. Now if your index is twice as large and the pages twice as many, then it takes longer to access the data. Now DRAM has a Strobe and the length of the strobe is how long the rows and columns can be left open before they must be refreshed. There is not enough time for the dram to be refreshed and then accessed with 4GB at the full access speed of the DRAM. The chipsets are optimized for 2GB, not 4GB and for 2 DRAM slots, not 4 DRAM slots populated. You can overclock the FSB (and hence the Memory Controller Hub = MCH) to gain some extra bandwidth and thus access the capabilities of the DRAM since the chipset is now clocked up. Usually when you clock up the FSB and concurrently the Memory Controller Hub (MCH) you need to raise the voltages of the CPU/MCH a bit as well.


You might have to force the Northbridge to run a bit faster to accept the DRAM. What I am doing below is dropping the CPU Multiplier from your E6850 default of 9 to 8 and raising your FSB from 333 X 4 (QDR) = 1333 to 375 X 4 = 1500. Both give you a Core Speed of 3.0Ghz but the 1500 FSB will force the Northbridge to run a bit faster and along with the slight MCH voltage increase, may bring you stability.

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I advise you to drop your DRAM speed to 667Mhz as you could well end up with motherboard memory controller issues in the longer term. Very possibly after your warranty is over.


With regards to testing the DRAM for Warranty purposes, you can test the DRAM at 800Mhz with the required voltage and test single modules. If you find an error with a module, then you can send in the pair for RMA. If you find issues with two modules (Dual Channel Mode) then you have an issue with the motherboard memory controller. If you find issues with four modules, then you have an issue with the motherboard memory controller.


I think you will find that in time your motherboard memory controller will degenerate since you are already finding issues which is why I advise you to drop the DRAM speed.

You will always have a lifetime warranty for the DRAM if you find issues on Memtest on single modules. To find two modules erroring out almost always is external to the DRAM. Not always as there can be the anomaly where two modules are in error, but it is not likely.


At any rate, good luck if you continue to run with 800Mhz and four DRAM modules.


Uh-oh. So I should drop the DRAM speed to 667Mhz. Is it technically possible to run these modules at 4-4-4-12 on 667Mhz or Mhz and latency are strictly proportional?


What I found interesting is in the BIOS, when the four modules were left on AUTO and I opened the DRAM Mhz menu, the speed was on 1200Mhz .. So I set it back to 800Mhz. Will check if I can set it to 667Mhz. :( Not really good news, but every expert here is saying the same thing: racing speed must be reduced when 4 modules are installed. :(( So it was an excellent decision to not overclock the CPU and FSB, RAMs, etc.. Lasted longer.


My next system I plan to buy will be a maxed out 4 or 2 or 1 module KIT - what is fastest - from Corsair on their website, tested to run at full-speed on best latency possible, near the max. memory capacity of the new DDR3 or DDR4 RAM supporting motherboard.

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Okay, will do. Thank you for this insight!


I'm wondering would it be too stupid in this case to try to overlock my system a bit, seeing it is a E8500 CPU easily able to run at 3.6Ghz *OR* this surely would mean even more load on the North Bridge / motherboard components causing circuits to deteriorate even more quickly?

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