MEMORY FAQ (please read before posting)

[chrisvsplumber_81]

Hey I was wondering what you all thought about my system and if you could help me identify my bottleneck. I got disgusted with Dell and fell in love with Crysis the game at the same time and gave my ispiron 531 a makeover. saved my money and got a amd phenom quad core 9950, motherboard: MSI k9a2 platinum 790 fx am2+, still have the HDD that came with the dell, the 19" monitor (max resolution 1440X900) and had 4 X 1 gig 667 ddr2 240 pin memory (5300u?) recently gave all my old stuff to my parents computer as it took them like 5 minutes just to load a web browser, and gave them two sticks of the memory. I'm going to get new memory but I have no idea if it would be worth just getting all new memory at 800 or 1022. Also as far as graphics go, is a bottleneck at my monitor's resolution? would it look more realistic with a better monitor? My brother told me it could have to do with the HDD speed? Also I don't know if this helps, but I was watching the frames per second and when I put the graphics options to the max my fps dropped to like 18 from 40....

one other side note, have any of you ever had your harddrive say that you're using WAY more gigabytes than you actually are? is this another blessing Dell has bestowed upon me,
if I've learned on solid piece of information of all this it's.... friends don't let friends buy Dell, wish someone woulda told me.
Thanks a bunch

 

[112inky]

Hi that was a wonderful list.. i am new to the forum and would like to have a happy time here... could anyone brief me about the modern developments in a systems memory?

 

[Proximon]

This is still great stuff, but we need an update for DDR3 with I7 and AM3.

 

[randomizer]

Agreed

 

[uberguber]

I have been building computers for quite some time now and long enough to know that things change quickly and constantly and my last build was about 6 mo. ago. In the past, I have had a soft spot for corsair's dual channel memory. I am getting ready for a build with water cooling and I am going to oc to the hilt. I mean extreme and I know most of the parts that I am going to use. As far as a higher and more stable oc, which mobo and ram combo do you recommend?
As for the water cooling, I will stick with Innovatek for the most part. Their the best in my eyes, but some of their stuff is out of stock, so I'll use some Koolance parts and so on. Eheim pumps are hard to beat.

 

[willclarke]

Q: How does memory access work, and what do the timings stand for?
A:
MEMORY ACCESS:
1. tRCD (RAS to CAS Delay) 2-3 cycles, The row is selected by the Memory Controller.
2. CAS (Column Address Strobe) 2,2.5,3 cycles (DDR), The Memory Controller selects the column and now the ROW is
ACTIVE, and the READ COMMAND is sent.
3. Data is sent to the DQ pins after CAS delay.
4. tRAS (Row address Strobe) 6 cycles, The module waits a certain period of time for the data to be active.
5. tRP (RAS precharge) 2 cycles, The Memory Controller DEACTIVATES the row.
6. Memory Cycle repeats as requested by the Memory Controller.

The timings are represented as follows:
2-3-2-6 1T (CAS, tRCD, tRP, tRAS)


---------


Sorry i don't understand this.

Is it better to get a 7-7-7-24 or a 9-9-9-24?

What is the difference between a 7-7-7-24 and a 7-7-7-21?

Couldn't understand the thread i am dyslexic so cannot read very well.

 

[Proximon]

When choosing DDR3, lower timings are always better, given the same frequency. Don't sweat the specific numbers too much. Lower is better in each case.

 

[willclarke]

When choosing DDR3, lower timings are always better, given the same frequency. Don't sweat the specific numbers too much. Lower is better in each case.

so the 4th number should be lower too? 21 is better than 24?

 

[Proximon]

Yes, but these are small changes.

 

[chaitanya_mkin]

WOW THATS GREAT MAN THIS POST HELP ME A LOT AND I INCREASED MY MEMORY KNOWLEDGE BY READING THIS MEMORY ARTICLE GREAT MAN GREAT THNXxxxxxxxxxxxxxxxxx

 

[zachanscom]

what's sa 2 memory?

 

[NateB]

I wish I read this thread before I began my research. It would have saved me a lot of time reading wikipedia entries about ram buffering.

this thread could do with an update, since ddr3 is out now....

What he said.

 

[dixit8611]

Is there any performance difference between DDR2 800 MHZ and DDR3 1333 MHZ or the difference purely lies in timing of the RAM ?
I am not talking about 2-3 % performance difference which is not even noticeable.
What is the effect of DDR3 or DDR2 or with changed timing on gaming?
I mean, should i go for DDR2 or DDR3 as i am building a new pc?I can buy a mobo accordingly if the difference is huge for gaming.
My current config is
GTX 260 sonic, AMD 550 BE, 600 watt PSU, (1440 * 900 ) monitor.
RAM and mobo i will buy.

 

[The_Prophecy]

This topic has been desticky in top of the forum by The_Prophecy

 

[brianzion]

Does anyone know where i can find a more detailed tutorial?
I am interested particulary in the phisical layout of the memory chip and how exactly the address and control signals work together to select a memory location. Use technical terms, i'm not affraid of them . thanks

try this http://www.passmark.com/products/rammon.htm

 

[brianzion]

A GUIDE TO UNDERSTANDING MEMORY

hi everyone here is a good ram program to help you identify your specs

http://www.passmark.com/products/rammon.htm

 

[gatortpk]

I'm not sure if this simple question is addressed specifically.

Can I always use a higher speed memory (same technology of course i.e. DDR3 = DDR3, and DDR2 = DDR2) as long as the CAS Latency is the same or lower?

Or more specifically, can I always use a lower CL rated module no matter how much higher the speed than is recommended specification? E.G. Can I always use a DDR3-1600 CL 6 (or same CL 7) in place of DDR3-1066 CL 7? (Or even DDR3-2000 CL 7 in place of DDR3-1066 CL 7?)

 

[Proximon]

The lower frequency and the HIGHER latency are always more compatible.

The compatibility of any given DRAM module is dependent on the MB, the MB BIOS, and the memory controller - which in modern systems resides in the CPU itself.

 

[gatortpk]

The lower frequency and the HIGHER latency are always more compatible.

The compatibility of any given DRAM module is dependent on the MB, the MB BIOS, and the memory controller - which in modern systems resides in the CPU itself.

I'm sorry, but that doesn't make any sense?

My system is a (late 2009) 27" iMac with 16GB of RAM. It has a Quad Core i7-860 @2.8GHz with hyperthreading.

The 2010 27" iMacs can take 32 GB of RAM now that 8GB SODIMMs are available, however mine doesn't seem to support it. The only difference between my iMac and the 2010 models (besides the slight speed bump) is that the newer iMacs take the DDR3-1333 SODIMMs. My iMac recommends the DDR3-1066 SODIMMs. I have read that I can actually put DDR3-1333 into my iMac but it has to have a CL of 7. The usual CAS Latency of DDR3-1333 RAM is CL 9. It has a first word read latency of 13.5 ns. Where as the CL 7 DDR3 has a first word read latency of 13.13 ns. (Slightly shorter/quicker read time)

I understand, the (slightly faster) speed of the RAM doesn't matter, it's the lower CAS Latency that matters more.

Is this not the case?

I am trying to figure out if the only reason that I haven't found anyone who has upgraded a late 2009 27" iMac to 32GB is because of the non-availability of DDR3-1066 8GB SODIMMs or the non-availability of DDR3-1333 8GB SODIMMs with a CL of 7.

If this is the only reason, then it would suggest that I can upgrade my iMac to 32GB, if I can find DDR3 RAM with a CAS Latency of 7 (or less, such as CL=6, that has a latency of only 9 ns).

 

[Proximon]

It's harder to produce CL7 1333 RAM than it is CL 9 1333 RAM. A DRAM module that can run at CL7 can ALWAYS run at CL8 or CL9 at the same frequency. Now, if your motherboard is so limited that it cannot detect the RAM, and has very limited ability to adjust, than I can see the scenario you describe occurring.

The Intel Memory controller on your CPU officially supports DDR3 1333Mhz CL9. That does not mean it cannot handle 1600Mhz CL8... but it's not officially supported, according to the product descriptions.

A particular motherboard may support a broad range of memory frequencies and timings. Think of your motherboard as the intermediary between the CPU and RAM. So your RAM could say "1333mhz CL7 1.65V" but your motherboard might not be able to understand that, or may not know how to adjust all the other settings that correspond to that description. But if your motherboard DID understand that, it would certainly understand more relaxed timings and frequencies.

So to repeat myself and elaborate, there are three things that determine compatibility. The memory controller on the CPU, the motherboard hardware, and the motherboard software (BIOS). The BIOS has to be programmed to handle that specific DRAM module, or at least default to settings that will work.

You asked, "Can I always use a higher speed memory (same technology of course i.e. DDR3 = DDR3, and DDR2 = DDR2) as long as the CAS Latency is the same or lower? "

The answer is, "No, you can always use lower speed memory as long as the latency is the same or higher, unless you have some strangely crippled system."

 

[Proximon]

This topic has been closed by Proximon