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RAM Timings of G.Skill RipJawsZ PC3-12800U CL7 on GA-MA790XT-UD4P BIOS

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February 14, 2013 3:18:34 PM

Hi!

I've gotten my hands on a set of "16GB-Kit G.Skill RipJawsZ PC3-12800U CL7", which is listed as having latency timings: CL7 (7-8-8-24). I'm not familiar with how to handle such technical details of RAM, but as I understand it, lower latency means (minimally) better performance.

When I plugged this kit in (mobo: GA-MA790XT-UD4P), CPU-Z recognized it as 16GB, but read the timings as CL 9, tRCD 9, tRP 9, tRAS 24, tRC 33, CR 2T, as well as dual channel.

Obviously, these numbers differ from the advertised 7-8-8-24. I'm also aware of the fact that XMP is a profile that's made for intel motherboards. My question is, is it recommended to configure these values differently, and how would I go about this?

CPU-Z reads JEDEC profiles as follows: http://imgur.com/56HqVxr

My BIOS has the RAM attributes structured as follows:
Attribute: SPD / Auto
CAS Latency: 9 / 9
RAS to CAS R/W Delay: 9 / 11
Row Precharge Time: 9 / 11
Minimum RAS Active Time: 24 / 29
...
Write Recovery Time: 10 / 12
Precharge Time: 5 / 6
Row Cycle Time: 33 / 40
RAS to CAS Delay: 4 / 5

I also don't understand why CPU-Z lists the max bandwidth as PC3-10700 (667MHz) (see image), even though the modules are PC3-12800.
For an inexperienced person, these naming conventions are incredibly confusing (the designations aren't very well differentiated).

Thank you.
a b } Memory
February 14, 2013 4:27:36 PM

enzym said:
Hi!

I've gotten my hands on a set of "16GB-Kit G.Skill RipJawsZ PC3-12800U CL7", which is listed as having latency timings: CL7 (7-8-8-24). I'm not familiar with how to handle such technical details of RAM, but as I understand it, lower latency means (minimally) better performance.


That's not a completely accurate assumption. Lower timing/latency means that the data cycle is shorter, thereby theoretically, making the data transmission to and from the CPU faster, but the actual performance will need to take into consideration the CPU's power/potential.

enzym said:
When I plugged this kit in (mobo: GA-MA790XT-UD4P), CPU-Z recognized it as 16GB, but read the timings as CL 9, tRCD 9, tRP 9, tRAS 24, tRC 33, CR 2T, as well as dual channel.

Obviously, these numbers differ from the advertised 7-8-8-24. I'm also aware of the fact that XMP is a profile that's made for intel motherboards. My question is, is it recommended to configure these values differently, and how would I go about this?
What you are seeing is the motherboard automatically selecting the specification for you. As you've discovered, the DRAM frequency(speed) is on "[Auto]", which means that the motherboard/BIOS will use the default values specified from the Serial Presence Detect (SPD) chip on your RAM.

enzym said:
CPU-Z reads JEDEC profiles as follows: http://imgur.com/56HqVxr

My BIOS has the RAM attributes structured as follows:
Attribute: SPD / Auto
CAS Latency: 9 / 9
RAS to CAS R/W Delay: 9 / 11
Row Precharge Time: 9 / 11
Minimum RAS Active Time: 24 / 29
...
Write Recovery Time: 10 / 12
Precharge Time: 5 / 6
Row Cycle Time: 33 / 40
RAS to CAS Delay: 4 / 5

I also don't understand why CPU-Z lists the max bandwidth as PC3-10700 (667MHz) (see image), even though the modules are PC3-12800.
For an inexperienced person, these naming conventions are incredibly confusing (the designations aren't very well differentiated).

Thank you.


RAM can be overclocked. Meaning, you can manually configure your RAM to operate at its full potential. This practice is done by changing a DRAM setting "[Auto]" to "[Manual]". Such settings are usually found on a tab in the BIOS/UEFI labeld "Advanced". There are several stickies on this forum that describe the gist of overclocking RAM and/or CPU. It is strongly recommended to read through this thread for more info on the terminology you'll encounter when venturing through your BIOS/UEFI. Then I recommend reading posts in this forum to understand the relation between RAM and CPU.
February 14, 2013 5:30:25 PM

Thanks for your input. So this is what memory overclocking is, already, then? I did not intend to overclock my memory. However, I would like to see my numbers match the ones the modules are designated as being (which is 7-8-8-24).

I skimmed over the MEMORY FAQ before the initial request for help, but it can be overwhelming when you have so many different terms without knowing how well you need to understand them in order to solve the problem. I was (roughly) aware of how RAM latency works, but don't know where to start with figuring out which timing values make for workable sets.

The confusion stems from three observations:
1) Why would memory be advertised as CL7, if CL7 is not the standard (not overclocked) setting it comes with, but requires overclocking to settle on these values?
2) Among the [Auto], [SPD], three JEDEC and one XMP profiles, none match the set of 7-8-8-24.
3) These terms have more than one entry in BIOS under slightly different designations, and I've found them assigned differently
Spoiler
RAS to CAS R/W Delay (Bios 9, 11)
RAS to CAS Delay (Bios 4, 5)
tRCD

Row Precharge Time (Bios 9, 11)
Precharge Time (Bios 5, 6)
tRP

Cycle Time (web), Row Active Time (web), Minimum RAS Active Time (Bios 24, 29)
Row Cycle Time (Bios 33, 40)
tRAS


The assumption I come out of this with is that the latency values should simply be set to 7 (CL/CAS, CAS Latency) - 8 (tRCD, RAS to CAS R/W Delay) - 8 (tRP, Row Precharge Time) - 24 (tRAS, Minimum RAS Active Time).
However, this set isn't represented in either of the profiles currently readable from CPU-Z or BIOS, and I'm deathly afraid of making a mistake.
Related resources
a b } Memory
February 14, 2013 6:51:51 PM

enzym said:
Thanks for your input. So this is what memory overclocking is, already, then? I did not intend to overclock my memory. However, I would like to see my numbers match the ones the modules are designated as being (which is 7-8-8-24).
This requires you to manually configure your DRAM settings in your BIOS/UEFI. The demand for better performance is always apparent, so RAM manufacturers are trying to keep up with demand, thus creating modules with capabilities that surpass the JEDEC standards for DDRX (where X equals the generation of DDR). This isn't quite overclocking RAM, but it's a start. The "rated" specs you see on the stickers or packaging of RAM is what the maximum stock settings are. By JEDEC standards, RAM has function within certain parameters, but even though this holds true, some people will go beyond JEDEC and manufacture specs. Doing so would be overclocking.

enzym said:
I skimmed over the MEMORY FAQ before the initial request for help, but it can be overwhelming when you have so many different terms without knowing how well you need to understand them in order to solve the problem. I was (roughly) aware of how RAM latency works, but don't know where to start with figuring out which timing values make for workable sets.
The FAQ is a good place to start so that you can either find the answer you're looking for, or, if need be, discover a better way to ask your question. I recommended reading through it so that questions like "how to I set my timings?" doesn't get asked. But since you've read through it, let's move on.


enzym said:
The confusion stems from three observations:
1) Why would memory be advertised as CL7, if CL7 is not the standard (not overclocked) setting it comes with, but requires overclocking to settle on these values?

Because RAM can be configured in so many variations, manufacturers will "advertise" the maximum potential you can expect out of the RAM in question. For example, G.SKILL manufactures hundreds of different models, so how do you choose among these hundreds? Well, you start by narrowing down the models that meet your desires. If you wanted RAM that can perform at 1866 MHz (for example), you wouldn't look at the models that cap at 1600 MHz. Similarly, JEDEC set the standard for what a RAM module has meet, minimally. This minimum is set as the default on the SPD chip, and is what is used when you simply plug and play.

enzym said:
2) Among the [Auto], [SPD], three JEDEC and one XMP profiles, none match the set of 7-8-8-24.
XMP is technology developed by Intel. The profile on the RAM is supposed to automatically set your RAM to it's manufacturer's max setting. The problem with this is that sometimes, the XMP profile will set your RAM at a higher voltage than necessary to reach the max settings.

enzym said:
3) These terms have more than one entry in BIOS under slightly different designations, and I've found them assigned differently RAS to CAS R/W Delay (Bios 9, 11)
RAS to CAS Delay (Bios 4, 5)
tRCD

Row Precharge Time (Bios 9, 11)
Precharge Time (Bios 5, 6)
tRP

Cycle Time (web), Row Active Time (web), Minimum RAS Active Time (Bios 24, 29)
Row Cycle Time (Bios 33, 40)
tRAS

The assumption I come out of this with is that the latency values should simply be set to 7 (CL/CAS, CAS Latency) - 8 (tRCD, RAS to CAS R/W Delay) - 8 (tRP, Row Precharge Time) - 24 (tRAS, Minimum RAS Active Time).
However, this set isn't represented in either of the profiles currently readable from CPU-Z or BIOS, and I'm deathly afraid of making a mistake.

You need not be afraid of changing the RAM specs. So long as you don't raise the voltage too high, you won't damage your sticks. If you make a change and it doesn't go well, the three typical scenarios are:

1. You'll receive an error message stating something about an overclock failure;
2. You'll have constant crashing in Windows (or other OS); or
3. You won't see any display on your monitor.

In either of these cases, you can easily reset your BIOS by either pressing F7 in the BIOS, or removing the CR2032 CMOS battery (it's about the size of a nickel) for about 30 seconds, and then reinserting it.
February 14, 2013 8:21:30 PM

So setting the values in BIOS to
CAS Latency (CL): 7
RAS to CAS R/W Delay (presumed tRCD): 8
Row Precharge Time (presumed tRP): 8
Minimum RAS Active Time (presumed tRAS): 24

Should be unproblematic (so far as you've outlined) and cover my concern, then?
What about the following four lines, which are displayed immediately below the above ones (I still don't fully understand why Precharge, Cycle and RAS to CAS Delay appear to have duplicates and what to do with them):

Write Recovery Time: 10 / 12
Precharge Time (?): 5 / 6
Row Cycle Time (?): 33 / 40
RAS to CAS Delay (?): 4 / 5

Is it possibly the case that 7-8-8-24 are the (not overclocked) maximum settings for each individual attribute instead of being a matched profile like the JEDEC profiles?
I'm still in the process of finishing reading the guides you linked to. It's a lot of information, and doesn't cut to the problem very directly. There's also the possibility that my impression that these values need to be in strict sets is a misconception.

Thanks again for helping me learn.
a b } Memory
February 14, 2013 10:11:35 PM

enzym said:
So setting the values in BIOS to
CAS Latency (CL): 7
RAS to CAS R/W Delay (presumed tRCD): 8
Row Precharge Time (presumed tRP): 8
Minimum RAS Active Time (presumed tRAS): 24

Should be unproblematic (so far as you've outlined) and cover my concern, then?
Yes.
enzym said:
What about the following four lines, which are displayed immediately below the above ones (I still don't fully understand why Precharge, Cycle and RAS to CAS Delay appear to have duplicates and what to do with them):

Write Recovery Time: 10 / 12
Precharge Time (?): 5 / 6
Row Cycle Time (?): 33 / 40
RAS to CAS Delay (?): 4 / 5


For now, do nothing.

enzym said:
Is it possibly the case that 7-8-8-24 are the (not overclocked) maximum settings for each individual attribute instead of being a matched profile like the JEDEC profiles?

Yes.

enzym said:
I'm still in the process of finishing reading the guides you linked to. It's a lot of information, and doesn't cut to the problem very directly. There's also the possibility that my impression that these values need to be in strict sets is a misconception.

Take your time. Rome wasn't built in a day. Understanding what you are reading is far more important than just adjusting your BIOS because you were told to.

enzym said:
Thanks again for helping me learn.

No problem. That's what this forum is here for.
!