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Keep memory voltage on auto?

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September 14, 2009 4:31:51 PM

I have my "Corsair XMS2 TWIN2X4096-8500C5 4GB 2X2GB PC2-8500 DDR2-1066 CL5-5-5-15" manually set in the BIOS to run at 1066MHz, 5-5-5-15, and with the DRAM voltage set to auto. I'm also using an ASUS P5Q Pro mobo.

Now, I read on many sites that I should set the DRAM voltage in the BIOS manually to 2.1V. I have it set on auto and everything seems to work perfect (stable and makes it past POST into windows). Should I set the DRAM to 2.1V even though auto seems to be doing the job? Also, when i do key in 2.1V in the BIOS the numbers turn yellow..a reason why I was a bit scared to set the DRAM to 2.1V.

More about : memory voltage auto

September 14, 2009 5:55:31 PM

Run some memory tests at auto voltage, if the memory passes all tests there's no point in upping the voltage.
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September 14, 2009 6:38:46 PM

Should I just use Memtest86+ ?
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a b } Memory
September 14, 2009 11:36:41 PM

Yes, and make sure you leave it running for at least 4-8 hours... many test for 20 min and think they are done... just FYI..
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a b } Memory
September 17, 2009 4:22:31 PM

I have a different opinion, doesn't mean it's right!

The RAM is designed to perform at 1066 and at those specs - only when it's getting 2.1Vs. By forcing it to those specs without giving it the voltage it requires, you're weakening its ability to work properly and without errors.

Let's compare the RAM to other electrical devices. I recently replaced the electrical motor at my lakehouse which lifts the boat out of the water. One of the major issues in these boat-lift motors is whether they're really getting the 110-120 Volts that they require to perform up to specs. Because many boathouses are some distance from the fuse box, the voltage delivered might be less than 110V. This makes the motor not work properly and it won't lift as much weight. It strains or fluctuates to lift a load that it could easily lift if given full voltage.

The same is true of the amps. Like RAM, these electrical motors want a given exact amount of voltage and a reliable draw of amperage to achieve the Watts of power they are rated at. Often you must use a 220V boat-lift motor instead of a 110V simply because the circuits (or wiring) in the home/boathouse are only rated at 15Amps. The way the electricity is delivered make it easy to combine two 110V circuits and give 220V at 15 amps on wiring that cannot support 110V at 20 amps.

When your PSU is overloaded, it's normally still putting out 5Vs and 12Vs, what it's lacking is amps - and the 2 combine and are called Watts. Watts means power. The RAM really wants X number of Watts. If it's not getting the Volts, I'm not sure that it's gonna draw enough Amps to make up for it - and it will certainly not last as long.

So, RAM isn't different from an electrical motor. It wants the power it was designed for. The warning color of the BIOS text is to make sure you're doing the right thing and not over-volting the RAM. In this case, you're doing the right thing by delivering the RAM the voltage it requires to operate properly.
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a b } Memory
September 17, 2009 4:34:31 PM

Mongox said:
I have a different opinion, doesn't mean it's right!

The RAM is designed to perform at 1066 and at those specs - only when it's getting 2.1Vs. By forcing it to those specs without giving it the voltage it requires, you're weakening its ability to work properly and without errors.

Let's compare the RAM to other electrical devices. I recently replaced the electrical motor at my lakehouse which lifts the boat out of the water. One of the major issues in these boat-lift motors is whether they're really getting the 110-120 Volts that they require to perform up to specs. Because many boathouses are some distance from the fuse box, the voltage delivered might be less than 110V. This makes the motor not work properly and it won't lift as much weight. It strains or fluctuates to lift a load that it could easily lift if given full voltage.

The same is true of the amps. Like RAM, these electrical motors want a given exact amount of voltage and a reliable draw of amperage to achieve the Watts of power they are rated at. Often you must use a 220V boat-lift motor instead of a 110V simply because the circuits (or wiring) in the home/boathouse are only rated at 15Amps. The way the electricity is delivered make it easy to combine two 110V circuits and give 220V at 15 amps on wiring that cannot support 110V at 20 amps.

When your PSU is overloaded, it's normally still putting out 5Vs and 12Vs, what it's lacking is amps - and the 2 combine and are called Watts. Watts means power. The RAM really wants X number of Watts. If it's not getting the Volts, I'm not sure that it's gonna draw enough Amps to make up for it - and it will certainly not last as long.

So, RAM isn't different from an electrical motor. It wants the power it was designed for. The warning color of the BIOS text is to make sure you're doing the right thing and not over-volting the RAM. In this case, you're doing the right thing by delivering the RAM the voltage it requires to operate properly.


So what's your point? We are debating if the value should be left on auto or manual.....
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a b } Memory
September 17, 2009 5:03:19 PM

Sorry, thought it was clear. I think the voltage should be manually set to 2.1V to provide the power the RAM requires to properly achieve the specs.
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a b } Memory
September 17, 2009 6:28:08 PM

Yea, true in most cases.... But I have seen 1066Mhz run fine on AUTO as well... Normally this can happen when the motherboard detects the RAM at 533 on first boot. If you see your 1066Mhz RAM as 800Mhz in the bios then yes it is a must to change it from AUTO to manual and adjust the frequency....
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a b } Memory
September 17, 2009 6:42:32 PM

What I'm saying is that if you send the correct recommended voltage to the RAM, by changing the typical default of 1.8V to in this case, 2.1V, that you won't have to adjust the frequency. In most cases, you cannot adjust the frequency to 1066 as long as the RAM is under-voltage.

Once you set the voltage to the correct value, the BIOS will normally see the RAM as 1066 rather than 800 and boot properly. Then you can go in and fiddle with timing and such.

As far as I know, and from my reading here, the Auto function on RAM voltage will never adjust to 2.1V from native 1.8V. The RAM isn't polled to determine what it should be.

Hey, I got my new CPU cooler and look forward to getting some advice on the OC settings. I'm reading over the Tom's guide to AMD OC and just installed Overdrive to make it easier to experiment. Once I get things running well, I'll go back and adjust the BIOS and drop the Overdrive. Hope things go well, if not, I'll be full of questions for you and the other OC guys.
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a b } Memory
September 17, 2009 7:19:14 PM

Mongox said:
What I'm saying is that if you send the correct recommended voltage to the RAM, by changing the typical default of 1.8V to in this case, 2.1V, that you won't have to adjust the frequency. In most cases, you cannot adjust the frequency to 1066 as long as the RAM is under-voltage.

Once you set the voltage to the correct value, the BIOS will normally see the RAM as 1066 rather than 800 and boot properly. Then you can go in and fiddle with timing and such.

As far as I know, and from my reading here, the Auto function on RAM voltage will never adjust to 2.1V from native 1.8V. The RAM isn't polled to determine what it should be.

Hey, I got my new CPU cooler and look forward to getting some advice on the OC settings. I'm reading over the Tom's guide to AMD OC and just installed Overdrive to make it easier to experiment. Once I get things running well, I'll go back and adjust the BIOS and drop the Overdrive. Hope things go well, if not, I'll be full of questions for you and the other OC guys.


Quote:
What I'm saying is that if you send the correct recommended voltage to the RAM, by changing the typical default of 1.8V to in this case, 2.1V, that you won't have to adjust the frequency. In most cases, you cannot adjust the frequency to 1066 as long as the RAM is under-voltage.


I understand what you are trying to explain here but that is not the case. For example, just cause you raise the voltage on the RAM does not mean that the frequency will automatically go from 400 to 533...

Normally a motherboard will default to the lowest frequency possible for stabilty purposes and it is up to the user to change the frequency to the desired value. Some boards will boot for the first time at 266/333 or 400 no matter what voltage you give it.... Of course this does not pertain to ALL boards but I would say most of them work this way, or at least all the boards that I have used...

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a b } Memory
September 17, 2009 7:41:21 PM

Well, let's take the case of the OCZ memory that both of us bought at one point, then returned. This memory required 2.2V to operate at 1066 mode - there's no doubt about that. If my motherboard had been able to send that voltage to the RAM I have no doubt it would have worked as per specs. As it was, with my board giving it only 1.8V to 2.1V, it will always come up as 800. This is also why OCZ is now selling 1.8V RAM of the same specs - too many boards can't deliver the 2.2V the other requires.

And yes, I'm claiming that if delivered the correct voltage, in most cases, the frequency will automatically go from 400 to 533 with Auto settings. It certainly works that way on most Gigabyte boards and from the responses here, it works on most. The Gigabyte board I have won't even let me manually over-ride the frequency setting if the SPD - coming from the RAM - says it's not supported. And the 533 SPD doesn't show up to the BIOS if the voltage is too low.

And what I'm saying also is that sending RAM the correct voltage is not over-clocking nor is it dangerous or damaging to either RAM or motherboard. It's simply doing what's required. And the Auto functions will never send the correct voltage to the RAM because there's no mechanism built-in motherboard BIOS (perhaps except Intel's XMS) that will auto-set the voltage. It's always something the user has to set.
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a b } Memory
September 17, 2009 8:13:44 PM

Yea, I guess it all depends on the mobo... For example, on my mobo the frequency will always default to 400 (800Mhz) upon first boot... No matter what I do If I want 1066Mhz I have to change it manually. Once I have the correct frequency then I go down to the volts and make the changes....

But yea I agree with you on that one, the only reason I stated otherwise is cause I normally use Asus/Asrock and EVGA motherboards and by what you have posted it looks like they work very differently =)
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a b } Memory
September 17, 2009 11:13:03 PM

'Optimal' is as fast as you can get it to run at as low a voltage as it takes to do so. I buy a lot of G.Skill F2-8500CL5D because it will always run well above rated specs, at well under rated voltage:


The comparison to an AC hoist motor is invalid. We're not talking about overloading an extension cord here... A stick of DDR2-800 pulls about a watt and a half; the 2.1 most fast RAM specs is a 17% overvolt - hardly appreciable. The higher speed causes it to dissipate more power as well - so you're probably looking at two watts (and notice that nearly all fast RAM is 'wrapped' in some sort of heatsink) - one third of what your tiny little night-light bulb consumes... Lower voltages do not 'stress' circuitry (higher voltages do - the term to google is 'electromigration' - it actually [gradually] eats the transistor junctions), the parts simply cannot reach the higher rated speed at JEDEC 1.8V...

You can always use faster RAM with any modern CPU/MOBO setup - you're just likely to have to set it up manually in the BIOS to take advantage of it. All DDR2 ram is actually DDR2/800; they 'speed-bin' it, i.e., test and select the sticks that will work at either lower (faster) latencies, or higher (faster) speeds, or both, and sell it at a premium as 2/1066, 2/1200, and so on. JEDEC spec'd RAM has a little EEPROM chip in it that stores the set-up information/tables for running it at 800 at various FSB (Front System Bus) speeds - has the preferred memory multiplier and timing info - this is called an SPD (Serial Presence Detect) just to confuse us; faster, higher rated sticks may (but don't necessarily) contain another set of tables (called an EPP - this one makes sense - Extended Performance Profile) that will tell the BIOS what multiplier/latncies to use at its higher rated speed - BUT - not all BIOS are created equal: some will read this EPP automatically, and set the RAM at the higher speed; some will require intervention (on a lot of Gigabytes, it's "Load Optimized Defaults" [but, to keep it more confusing - not all BIOS with the "Load Optimized Defaults" fuction actually use it to set the EPP]), and some just plainly don't know the EPP exists (if it does) and you have to set the higher speed manually!

You have control over the basic system clock (I'm going to cal it B_CLK), once you start manually timing the MOBO through the BIOS. B_CLK times four is your FSB (once again, Front System Bus); B_CLK times your memory multiplier is your DRAM rate; B_CLK times your CPU's multiplier is your CPU frequency.

Examples: if you set your system clock to 333, you will need a 2.4 memory multiplier (333 x 2.4 = 799.blahblahblah) to run your RAM at 800, and if the CPU multiplier is, say, 8.5, you will get a CPU clock of 2.83GHz; at that same B_CLK you would need a memory multiplier of 3.2 (3.2 x 333 = 1065.6) to take advantage of 1066 RAM. Now, lots of CPUs that are rated at a 1333 nominal FSB will run a lot faster, sometimes with a little more 'oomph' from a voltage increase; for example, I run a Q9550 that is rated at 1333 FSB (333 B_CLK) times an eight point five multiplier, for a 2.83GHz speed. It will comfortably run with the B_CLK well over 450 - and here's where faster RAM comes in. The smallest RAM multiplier available from a MCH (Memory Control Hub - or 'NorthBridge') is 2.0, but, with a 2.0 multiplier, that means at a 450 clock, your RAM will need to run at 900 (again, 450 B_CLK x 2 = 900), which most 800 RAM just won't do! This is referred to as a 'RAM limited bus', meaning the CPU can't run a B_CLK any higher than (roughly) half the RAM's available speed - and thus, the need for faster RAM. Mind you, this only applies if you both can, and intend to, run your FSB above 1600 (once again, a B_CLK of 400+ times 4 gives you a 1600+ FSB)...

To further complicate matters, people often misunderstand the actual quantitative speed improvements inherent in faster ram... Here's the mistake: 1066 is 33% higher than 800 ([1066-800]/800 = 266/800 = .33), so 1066 RAM must be a third faster than 800, right? Not so! You have to figure in latencies. Most 800 will run at 4-4-4-12, while most 1066 is rated at 5-5-5-15, or, even worse, 5-5-5-18. Here's how to appraise the situation in reality: at 800 MHz, a RAM bus cycle is 1.25 nSec long (1000/800); at 1066 (1000/1066), it is roughly .938 nSec long - so, with an 800 stick at a 4 average latency, a RAM bus transaction takes 1.25 (cycle time) times 4 (latency), or 5nSec, while at 1066 it is .938 (cycle time) times 5 (latency), for a transaction time of (roughly) 4.7nSec - so you see, by going to nominally 33% faster RAM, you actually gain three tenths of a nSec per transaction - .3 (transaction gain) over 5(transaction total) = .06, for a real-world improvement of 6%. The main function of fast RAM is to give you more 'headroom' to OC your CPU!


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a b } Memory
September 18, 2009 12:10:55 AM

Thanks bilbat - that helps a lot. Dang, thought that hoist example was pretty good!

One thing I don't seem to have on my Gigabyte board is the ability to manually change the MHz of the RAM. Nor does it give you anything but the ability to reduce the RAM multiplier from the defaults. I'm playing with changing the Bus speed a tiny bit to move the RAM from 533 to 555 - which is the SPD rating for my PC8900 RAM.

Interesting discussion here!!!
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September 18, 2009 1:04:32 AM

wow i come back a few days later to find ALL this!! I'm gonna read everything and get back to you guys. I havent had the time to do Memtest86+ yet.
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September 18, 2009 1:20:39 AM

OvrClkr said:
Yea, I guess it all depends on the mobo... For example, on my mobo the frequency will always default to 400 (800Mhz) upon first boot... No matter what I do If I want 1066Mhz I have to change it manually. Once I have the correct frequency then I go down to the volts and make the changes....

But yea I agree with you on that one, the only reason I stated otherwise is cause I normally use Asus/Asrock and EVGA motherboards and by what you have posted it looks like they work very differently =)


My Asus p5q pro set the ram to default 400mhz. So what i get from the posts is that i should manually set my ram to 2.1V? rather than keep it on auto.

wow bilbat's post seems very technical! You really know ur stuff. If theres one thing i get from that post is that im happy i got 1066 ram! because I overclocked my CPU to 3.8ghz = 1700 FSB!
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a b } Memory
September 18, 2009 3:32:19 AM

yes, set to 2.1V... if you use the program CPU-Z it should show the SPD data - it should show the recommended voltage at various speeds (533, 400, etc..) and the timings at those speeds. Run a tester like Prime95 for several hours. If it completes fine at 2.1V, try it at lower voltages. And if all works great at the lower voltage, stick to it!
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a b } Memory
September 18, 2009 1:05:23 PM

I have found CPU-Z to occasionally miss or misrepresent data in the SPD, and it does not list all the registers you need to see to be able to properly set up a MOBO; MemSet's SPD page is better:
http://www.tweakers.fr/download/MemSet41b4.zip
and if you're really astute, and say, discover that your tRFC will run fine at 52 rather than the 60 in the SPD, and want to edit it so it will ever after be read that way:
http://www.softpedia.com/get/Tweak/Memory-Tweak/SPDTool...
will let you write to the SPD itself!
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