DDR3 Memory Standards: Blurry Lines

Question

DDR3 Memory Standards: Blurry Lines
Rated speed, JEDEC, XMP, EPP, overclocking, overvolting... and what it all means
Much confusion has dawned upon many new users.  Purchasing memory is not as easy as it used to be.  Manufacturers have forced belief that their modules run at certain DDR3 standards.  However, what they don't tell you is that these standards [1866, 2133] do not exist.  You're required to overclock, modify timings, and overvoltage the memory modules that have these manufacturer rated speeds.  So when you plug your memory into your computer and boot it up for the first time, do not expect 1600+ speeds the first time around.  You'll at least have to enable XMP/EPP and/or manually configure (timing and voltage) settings in the BIOS.
Now this is where things start to get complicated and full of numbers:
JEDEC:
JEDEC is an industry memory standard specification.  Manufacturers comply with the JEDEC standard by programming the JEDEC profiles into the SPD chips on the memory.  The highest SPD profiles you will find on the market right now are DDR-1333 (some are DDR-1600, but DDR-1333 is the main).  This is because the latest Intel CPU platform [Sandy Bridge - P67] doesn't support higher than DDR-1333.  This will change in the future, as Ivy Bridge supports DDR-1600 I believe.
EPP (Enhanced Performance Profile):
EPP is NVIDIA's higher-level SPD programming extention.  NVIDIA's nForce chipsets can read this SPD extention to provide the much desired "one click overclock."  Change a setting and wala, auto-overclocked memory.
XMP (eXtreme Memory Profile):
XMP is Intel's version of EPP that runs on Intel chipsets.
NOTE:  EPP and XMP have 2 requirements:  your memory MUST have an EPP/XMP profile, and your chipset MUST support XMP/EPP.  There are no exceptions to this rule.
The point of all this confusion, and why the manufacturers do it
The most obvious question is why do the manufacturers do all this?  Because they want to make more money.  The bigger numbers on the sticker means bigger sales.
You would wonder why JEDEC have allowed Intel and NVIDIA to decimate their standard with their "extensions", but nonetheless this is what we're stuck to dealing with.
Example scenarios
Example 1:
You bought a P67 board, 2600k and some DDR-2133 memory.  You build the computer to find that the memory isn't running at its manufacturer's rated speed (2133), so you take the first step:  enabling XMP (this is an Intel chipset, remember) in the BIOS.  However, your memory lacks the XMP profiles in its SPD chip so you can't change the setting.  You would then consult the manufacturer's website for the settings to be used.
Example 2:
You visit the manufacturer's website, and consult their specified timings for your memory.  I've chosen Corsair's Dominator GT 2133C9 in this case (>link here<).  If you go to the tech specs section, you shall notice that the SPD speed is 9-9-9-24, DDR-1333, 1.5V which is a JEDEC standard.  Corsair's "tested" speed is 9-10-9-27, DDR-2133, 1.65V* which is not a JEDEC standard, but is programmed with DDR-2133 as an XMP profile.
What this tells us is that these are DDR-1333 modules overclocked to DDR-2133 and programmed with an XMP profile to support that without manual adjustment.  The actual speed of the module is DDR-1333, but the manufacturer's rated speed is DDR-2133.  Like I said previously, manufacturer's rated speeds require at least entering the BIOS and either; enabling XMP, or manually configuring timings, voltage and speed.
If you bought the Corsair modules and tried to run them on an AMD Phenom II system, you would have to input the timings, voltage and speed manually because AMD chipsets do not support XMP.  This is a common misunderstanding among many AMD-related visitors of the forum.
Summarising post and final thoughts
To summarise:
- The JEDEC standard of DDR-1333 is currently the highest support on Intel's Sandy Bridge platform.  Therefore, whether your memory has regular SPD profiles for DDR-1600+ or not, it will NEVER be set at those speeds.
- Understanding the difference between JEDEC standards and manufacturer's rated speeds.  The best hint would be look at the voltage.  *JEDEC standards will always be 1.5V or lower; never 1.65V or higher.
- For your memory to work at its manufacturer's rated speed out the box you must; 1) have an XMP/EPP compatible chipset, and 2) have XMP/EPP profile(s) on the memory.
- AMD users will be unable to take advantage of XMP's convenience since their chipsets do not support it.  They will have to set their settings manually.
I hope that this has explained a lot of things to some people, and increased their understanding.
Thanks for reading.
Another question to ask yourself: do you really need more than DDR-1333 to begin with?  Find some answers and draw your own conclusion - >> P67 & RAM Performance -or- Why DDR3-1333 RAM is enough -> Save the money! <<

Answer 1

Quote from: Bas on 31-May-11, 23:57:20
@doubleohseven, you may want to read this before making more statements that involve lawyers and such: >>Please read and comply with the Forum Rules.<<
Further more, you are totally on the wrong track.
1. The memory controller is INSIDE the CPU, as such the CPU is the engine of your car.
2. The memory controller is GUARANTEED by Intel (AMD is about the same) to do 1333.
3. Memory is the tire of the car, it needs to be fast enough, but if the engine fails to do that speed the tires will NEVER reach their rated speed.
4. The motherboard is the chassis of the car, it provides mounting points but it doesn't power the car.
5. The harddisk is the trunk of the car, it determines how much load you can carry/store
6. The videocard is the windscreen and wipers of the car, the bigger they are the more details you see in gaming
7. The PSU is the petrol-tank of the car, use a too small one and your machine stops way before reaching your target.
Maybe now you have a clue that you are on the wrong track?
Sadly people don't do their homework before buying stuff, as such they do not know what they are buying and end up frustrated because they think something is wrong.
Ram is just 1 component....there is also more to a car then just a tire.
No, actually I think I am pretty much on the right track.  Yes the memory controller on the CPU is 1333.  But if you read the OP, you can see that what he describes (and what I found out) is that the chips on our RAM are actually 1033, 1333, and sometimes 1600 chips, overclocked from the factory to the speeds you buy and pay for ("What this tells us is that these are DDR-1333 modules overclocked to DDR-2133 and programmed with an XMP profile to support that without manual adjustment.  The actual speed of the module is DDR-1333, but the manufacturer's rated speed is DDR-2133.  Like I said previously, manufacturer's rated speeds require at least entering the BIOS and either; enabling XMP, or manually configuring timings, voltage and speed.").  Therefore, this can cause instability with the system, I believe if the chips on the RAM were actually at the speeds advertized (1600, 1866, 2133), we would have a much greater chance (of course not 100% guaranteed because of the CPU) of running at those speeds.  If the CPU was strictly what is limiting the RAM, wouldn't EVERYBODY on a Sandy Bridge system not be able to get their RAM up to 2133, because I AM seeing plenty people do you.  The CPU may be ONE factor, but the RAM not having the chips on board at advertized speeds is another factor.
As for the lawsuit, seriously...  I was just venting, it was more of a rhetorical statement, being angry about the RAM issue.  If you have a problem with the post, please delete it.