Calculating vram mhz from the access time rating

[Omar85]

Would someone please be so kind as to explain how to get the maximum (theoretical) memory speed (MHz) from graphic card memory chip's access time rating in nano-seconds?

I can't seem to work it out.

Thanks

- Omar

 

[Viper96720]

I think its ns 1/X(1000)
So 3ns would be hit 3 press the 1/x key and multiply by a 1000 and you get 333.333

 

[Omar85]

ah, that seems right.

Thanks a lot

 

[BoomAM]

Hi,
Are you sure thats it, cos the example youve given for 333mhz aint right, if i remember correctly, then 5ns is 333mhz

 

[Omar85]

Originally posted by: BoomAM
Hi,
Are you sure thats it, cos the example youve given for 333mhz aint right, if i remember correctly, then 5ns is 333mhz

Hi BoomAM,

My curiousity was raised from this article:

http://www.digit-life.com/articles/sumagf4ti/index.html

About 1/6 th the way down the page, they have the memory on the graphics cards along with ns ratings and theoretical maximum clock speeds in mhz. I couldn't figure it out on my own.

Using those two as examples:

(1 / 3.6) * 1000 = 277.77...... (the article says 275 ...which is kinda right)

(1 / 2.8) * 1000 = 357.14...... (the article says 357, which is correct)


I've also seen articles mention 4 ns as 250 Mhz.


Btw...as regards to DDR memory on graphics cards...those values are doubled to show the DDR rating.


On a second reading, your 5 ns for 333 might be correct.... as (1 / 5) * 1000 = 200 Mhz * 2 (DDR) = 400 Mhz (maximum)... therefore if it is a rating for a DDR chip, the 333 might be the "safe" clock speed for the chip.

I may be totally wrong though...so don't take my word for it ;-)

- Omar

 

[pillage2001]

F = 1/t, where F is the frequency and t is the time. That's all you need to know.

 

[blade2]

Originally posted by: pillage2001
F = 1/t, where F is the frequency and t is the time. That's all you need to know.

just to verify that and that t must equal seconds not nanoseconds, that is __ns to the power of -3, e.g. 3ns= 3 to the power of -3 or 0.003s

edit: didnt make sense!

 

[pillage2001]

Originally posted by: blade2

Originally posted by: pillage2001
F = 1/t, where F is the frequency and t is the time. That's all you need to know.

just to verify that and that t must equal seconds not nanoseconds, that is __ns to the power of -3, e.g. 3ns= 3 to the power of -3 or 0.003s

edit: didnt make sense!

ns = E-9
us = E-6
ms = E-3
s = E0

 

[Omar85]

since this thread is a bit popular, could anyone please try to reply to my other thread regarding leadtek ti4200 cards please?

http://forums.anandtech.com/messageview.cfm?catid=31&threadid=920809

Thanks

- Omar