What is memory frequency ?

[Houdini]

Hi !

You know along with capacity memory has its frequency , but it has no processing unit inside(only memory sectors for temporal information), so what part of memory determines its frequency ? I think none of RAM parts

As I see it , memory frequency is a ability of memory to operate with CPU at maximum of certain numbers, so it depends on CPU rather than on memory right ?
but not only on CPU , also you can decrease that from BIOS , and make RAM operate only at 1666mhz for example , if so then is memory frequency same as RAM slot bandwidth ?
if yes , why memory manufacturers write numbers on memory at all , if it never actually depends on memory itself.

 

[dragontamer5788]

no processing unit inside

DDR4 has a pretty complicated protocol actually. DRAM in general has the information obliterated on any read. The capacitors holding the information can only be read once before they run out of electricity. Furthermore, DRAM can only hold information for ~15 milliseconds before they run out of charge. DDR4 RAM needs to be constantly controlled... refreshing the data every 15 milliseconds as well as rewriting the data whenever it is read.

so what part of memory determines its frequency

The frequency is the communication bus. The actual speed of the RAM is dependent on the operation. If you've heard of "CAS Latency", that is the "Column Access Strobe" part of the DDR4 protocol. "CAS Latency" is a closer measurement of speed with regards to what the actual RAM.

The typical RAM read happens as follows:

Step 0: Precharge. Sets all sense amplifiers to a neutral voltage, in preparation of step 1. Often done simultaneously with other steps
Step 1: RAS: Row Address Strobe. This copies one "bank" of data into the sense amplifiers (1024 or 2048 bytes in DDR4). Sense amplifiers can be read/written without losing information. By reading the RAM, the data is obliterated in the DRAM cells.
Step 2: CAS: Column Address Strobe. "CAS Latency". This reads ~64 bytes out of the ~2048 bytes that were copied to the sense amplifiers from step #1
Step 3: Close row. This copies the data from the sense-amplifiers back into the DRAM cells. Step 0 often happens simultaneously with this step.

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The "frequency" is simply the speed that the CPU communicates to the DDR4 chips to issue these commands. The actual speed of a step is a "memory timing". There are many, many commands and many different timings associated with them. Your DDR4 chips internally tell the CPU how fast they are through XMP profiles (and standard JEDEC timings for fallback).

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EDIT: For further details, see https://www.systemverilog.io/ddr4-basics#bg-ba-row-col

 

[Houdini]

DDR4 has a pretty complicated protocol actually. DRAM in general has the information obliterated on any read. The capacitors holding the information can only be read once before they run out of electricity. Furthermore, DRAM can only hold information for ~15 milliseconds before they run out of charge. DDR4 RAM needs to be constantly controlled... refreshing the data every 15 milliseconds as well as rewriting the data whenever it is read.



The frequency is the communication bus. The actual speed of the RAM is dependent on the operation. If you've heard of "CAS Latency", that is the "Column Access Strobe" part of the DDR4 protocol. "CAS Latency" is a closer measurement of speed with regards to what the actual RAM.

The typical RAM read happens as follows:

Step 0: Precharge. Sets all sense amplifiers to a neutral voltage, in preparation of step 1. Often done simultaneously with other steps
Step 1: RAS: Row Address Strobe. This copies one "bank" of data into the sense amplifiers (1024 or 2048 bytes in DDR4). Sense amplifiers can be read/written without losing information. By reading the RAM, the data is obliterated in the DRAM cells.
Step 2: CAS: Column Address Strobe. "CAS Latency". This reads ~64 bytes out of the ~2048 bytes that were copied to the sense amplifiers from step #1
Step 3: Close row. This copies the data from the sense-amplifiers back into the DRAM cells. Step 0 often happens simultaneously with this step.

----------

The "frequency" is simply the speed that the CPU communicates to the DDR4 chips to issue these commands. The actual speed of a step is a "memory timing". There are many, many commands and many different timings associated with them. Your DDR4 chips internally tell the CPU how fast they are through XMP profiles (and standard JEDEC timings for fallback).

--------

EDIT: For further details, see https://www.systemverilog.io/ddr4-basics#bg-ba-row-col

lets say we have 1 system to test 2 difderent memory modules and
why same manufacturer ddr4 modules maxing freq at 2666 or 3333 mhz , if they are same , what those 2 have different phisically?

 

[dragontamer5788]

lets say we have 1 system to test 2 difderent memory modules and
why same manufacturer ddr4 modules maxing freq at 2666 or 3333 mhz , if they are same , what those 2 have different phisically?

I don't think you understand. Let me repeat myself:

The "frequency" is simply the speed that the CPU communicates to the DDR4 chips to issue these commands. The actual speed of a step is a "memory timing". There are many, many commands and many different timings associated with them. Your DDR4 chips internally tell the CPU how fast they are through XMP profiles (and standard JEDEC timings for fallback).

Even with the same frequency, you may have different memory timings. "Frequency" is the speed at which the CPU talks to DDR4 RAM. It is the speed of communication. The speed of the DRAM itself is a memory timing, such as CAS Latency.

 

[Houdini]

pf.... so 1 stick corsair 16gb module costs 100$ and it is 2666 mhz
another corsair 16gb stick is 3333mhz costs 150$.

So youre saying they physically same 100% , then why im paying +50$ .
am paying for "many difderent commands" or what?
i will try to rephrase question , how ddr4 2666mhz memory stick are restricted internaly compared to ddr4 3333mhz?

 

[dragontamer5788]

So youre saying they physically same 100%

You are misunderstanding something. I never said that.

how ddr4 2666mhz memory stick are restricted internaly compared to ddr4 3333mhz

A 2666 MHz clock will have a slower communication channel to the CPU than the 3333 MHz RAM.

Whether or not the DRAM is faster or not is a different question, one that is better answered by a statistic called "CAS Latency" (among other memory timings). There's a lot of different speeds to RAM.

 

[Houdini]

that slower communication channel , physically exists where? inside RAM stick or on motherboard?

 

[dragontamer5788]

that slower communication channel , physically exists where? inside RAM stick or on motherboard?

Depends on your computer.

AMD chips synchoronize that communication channel into infinity fabric itself, so the memory channel speed affects AMD Chips (cross CCX communications), the Motherboard, and the DDR4 RAM. Highly clocked RAM has been shown to increase power in Zen1 chips for this reason. (Probably still true in Zen2)

Intel runs the clock independently, so its just the motherboard and RAM I guess for Intel-based computers.

 

[Houdini]

if RAM stick is not restricted inside by anything , it means 2666 and 3333 RAMS are 100% ident , then why 3333 costs more ? it should have some internal frequency blocker or something like that. they should be built difderently at least.

dragon , youre desperately complicating things ...
my question is so simple .

 

[xman2007]

if RAM stick is not restricted inside by anything , it means 2666 and 3333 RAMS are 100% ident , then why 3333 costs more ? it should have some internal frequency blocker or something like that. they should be built difderently at least.

dragon , youre desperately complicating things ...
my question is so simple .

It's programed as a standard inside the ram and the motherboard reads the programed data when the computer starts and sets it accordingly upon first boot or whatever you set the ram to in the bios, jedec specs are typically the standard /default settings, that's what post does amongst other things

 

[Houdini]

It's programed as a standard inside the ram and the motherboard reads the programed data when the computer starts and sets it accordingly upon first boot or whatever you set the ram to in the bios, jedec specs are typically the standard /default settings, that's what post does amongst other things

if it is programmed internally in RAM stick , does it mean that its frequency is artificilly truncated by manufacturer , purely for marketing purposes?

 

[basco]

you pay more for 3333 because manufacturer tested it if the 2666mhz stick can run at these higher frenzys-not all will run at 3333mhz with certain volts.
so maybe one stick will be a 2800 or 2933 or 3200cl14 .

my 4000cl19 stick is a 2133mhz bin tested by patriot to run at 4000mhz but you could rewrite the spd

you pay for the binning process because not all samsung 2133mhz will run 4000.
so patriot buys a bunch 2133 sticks and bins them to different levels

 

[Ferrum Master]

if it is programmed internally in RAM stick , does it mean that its frequency is artificilly truncated by manufacturer , purely for marketing purposes?

Are you trolling or what? Silicon is and always was graded into tiers, basing how fast/stable they go. Certification at these speed tiers makes the differentiation. It is much harder to get higher speed modules and have them the same. That's why the additional cost.

 

[Houdini]

Are you trolling or what? Silicon is and always was graded into tiers, basing how fast/stable they go. Certification at these speed tiers makes the differentiation. It is much harder to get higher speed modules and have them the same. That's why the additional cost.

I'm not trolling , just a questioner looks like unlike some, you don't want to see question ? it's your problem
that's how question was derived , it's physical difference or just a programed restriction inside? planks are tested and guaranteed frequency is 2666 , above it's unstable, ok! But maybe radiator will do the job ? and let's say with radiator it goes higher and stable.
So, when you are told that you can buy RAM for 300$ instead of 150$ only because it's programmed internally like that it means you pay extra for radiator over your RAM , but not because it's build differently.
Again, same wires and same stones. Even same amount of wires and same amount of stones, is it superhard to understand for you ?

 

[0xCats]

Lets do it like this.
Explain to me what you think memory is and how it works as best as you can.
Then I have an idea of what the misconceptions are that you have and can correct them.
If you do it well enough I'll give you the version from someone with VLSI experience?

Sound good?

 

[Ferrum Master]

it's physical difference or just a programed restriction inside? planks are tested and guaranteed frequency is 2666 , above it's unstable , but maybe radiator will do the job ? With radiator it goes higher and stable.

There is no place to implement the restriction in the first place. Look at the construction and protocol. Documentation are available even for most IC's that reside on the RAM stick.

I guess the problem is at your end, thinking someone puts some sort of barriers. You have to pay to premium, just because it is more rare and harder to produce. It applies to most things. Not only semiconductors.

To be short... someone ie the whole industry is not trying to scam especially you. You can get exactly what you paid for. A guaranteed speed limit upon what you can use your customer/buyers rights, when something is really off.

 

[Houdini]

Ferrum Master

I'm not saying they try to lie , the things are what they are , that's it.

that reminds me situation around Quadro and Geforce. it was long time ago, one dude made it to install quadro drivers on Geforce card , guess what ? card started to work like Quadro.. scam ha ?
now you're unable to do that even if you will die of installing it, but GPUs are same story , same vRAM stones and wires, almost same CUDA cores but 3-4 performance boost in certain applications, only drivers and minor stuff differs , so +3000$ for drivers ? Good deal. oh yes error correcting code that no one needs !

I'm not saying RAMs should arrive at maximum speeds all of them , only thing I'm saying is that are restricted artificially (for stability reasons whatever , but one manufacturer sticks ARE NOT MADE FROM DIFFERENT STONES for handling different speeds)

0xCats

RAM has only places for holding info inside , no processing unit inside, it means RAMs mhz is something that is not related to RAM directly but related to CPU and MB
So 2666is just a rate in which CPU can fill info inside that RAM. (let's say abstractly : 2666mhz = 5630k at 3000mhz can fill whole RAM stick in 1 second ) you go lower like 1333 , it will take 2 seconds to fill it, so it means it's nothing more than a bandwidth between CPU and RAM that physically are wires on motherboard.

so ddr4 standart is belong to motherboard at first place (if bus can handle 10000mhz we have to wait RAM manufacturers to come with something that will be close to that speed and ensure stability).
that's how I see it.

 

[Caring1]

my question is so simple .

If it's so simple, figure it out yourself, and stop posting trying to sound intelligent and refuting everything people reply with.

 

[xman2007]

It depends on the chips first and foremost, so no all ic's are not the same are are not only distinguished by the cpu and memory controller, the ram chips are rated for a certain speed and some are binned to achieve higher rates, that has nothing to do with the cpu or chipset or imc, only after that do these things play a part, not sure what more info you need, but I think this is my last post on this

 

[TheLostSwede]

@Houdini you're pulling our legs, right?

Since you seemingly has such a bad understanding of how it works, I suggest you read the below page on Wikipedia before you continue.

Dynamic random-access memory - Wikipedia

en.wikipedia.org

 

[95Viper]

Alright, stop the insults and other crap.
Get on topic.

Any more guideline violations and this thread is going to be closed and points ( or worse) may be doled out.