Effective memory clock

[easyfreezy82]

In pcpartpicker with graphic cards it talks about effective memory clock in a graphic cards description. What is that?

[5x5]

The actual speed at which the memory runs.

[Chett_Manly]

9 minutes ago, easyfreezy82 said:

In pcpartpicker with graphic cards it talks about effective memory clock in a graphic cards description. What is that?

The graphics card is likely using double data rate memory, DDR, and with that they will have an effective memory clock that is twice the actual memory clock, since its double data rate.

 

Its like with PC memory too, I have my memory running at an effective rate of 2800mhz, but its actually 1400 mhz doubled.

[Oshino Shinobu]

9 minutes ago, 5x5 said:

The actual speed at which the memory runs.

That's the actual/physical speed. Effective speed is when DDR and other factors are accounted for. 

 

GDDR4 and higher (I believe, it may be true for others as well) performs 4 operations per cycle. If the actual clock speed of the RAM is 1000MHz, the effective clock speed is 4000MHz. 

 

There's some confusion, as it actually has three different clock speeds that can be quoted. Different programs show different things. Manufactures will pretty much always quote the effective clock speed, which is the actual clock speed x4. Most system monitor and overclocking programs will show the actual clock speed, which is multiplied by 4 to get the effective clock speed. There are also some, however, that show another clock speed, which is half that of the effective speed. This is a clock speed that accounts for how GDDR RAM works, but does not account for DDR.

 

I have a longer post somewhere that explains the RAM clockspeeds in more detail. I'll see if I can dig it up.

 

EDIT: Can't find it. There's some details on it on the GDDR5 Wiki page. It's the parts that cover CK and WCK. For the most part, you don't need to know it, but there's a common misconception that it works in the same way as standard DDR RAM.

 

https://en.wikipedia.org/wiki/GDDR5_SDRAM

[mariushm]

DDR2 and DDR3 transfer 2 bits per clock ... so a 1000Mhz chip will be advertised as 2000Mhz

GDDR5, GDDR6 etc transfer 4 bits... so a 1000Mhz chip will be advertised as 4000Mhz

 

so the actual frequency isn't used because it would only confuse... you'd get a GT210 card with 1 GB DDR3  listed as equally good in memory dept. with card that has 2-4 GB GDDR5.