Memory PC 2100 PC 2700 PC 3100 PC 3700

[pbrandao]

I need information abouth this formula for obtain speed in MHZ from memory DDR PC 2100 PC 2700 PC 3100 PC 3700
:confused:

[TheGr81]

Divide by 16.

PC2100 ~133MHz
PC2700 ~166MHz
PC3200 -200MHz
PC3700 ~233MHz
PC4000 -250MHz
:)

[pbrandao]

why divide by 16 ?.

[Thrax]

Because it does 2 8 byte calculations per cycle, or 16.

[qparadox]

The PC # rating is the theoretical bandwidth of the memory in MB/s.

So to calculate the PC number, X, for ram of Y MHz you do

X = Y Megacycles/s * 2 bits / cycle (since DDR) * 64 bits (this is the width of the bus) * 1 byte / 8 bits (this is just the way it is) ->

X=16 Y MegaBytes/s

So to go backwards you do Y=X/16.

I hope you like math :).

[madmat]

Personally, I'd just divide by 16 or if you want it's speed (as in ddr400) divide by 8 instead, example, pc3200/8=400. Simple, no?

[TheGr81]

:wow: I forget where I heard divide by 16 but I guess that explains it. I think... :scratch:

[sfleuriet]

Divide by 16.

PC2100 ~133MHz
PC2700 ~166MHz
PC3200 -200MHz
PC3700 ~233MHz
PC4000 -250MHz
:)

I could've sworn that my PC3200s were 333mhz..

well wait- i have one stick of PC2700 and one stick of PC3200 - that ADDS up to 366mhz (if thats how if would work..?) so maybe thats why I'm thinking of instead of 333mhz.

[shwaip]

all of your memory runs at the lowest speed of any one stick - you're running it all at PC2700 = DDR 333 = 166 MHz

[sfleuriet]

ohhhh yeah thats right!! i forgot about that completely... ok so its 332mhz mathematically, but my BIOS just says 333mhz. ok thanks

[shwaip]

it's 166.6 (repeating).

166.6 * 2 = 333.3

[sfleuriet]

ah ok so it does simply add up. cool

[shwaip]

They don't add. All the memory runs at the lowest speed...the speed of your PC3200 (normally DDR400) is PC2700 (DDR333) in your system, because you're running it with PC2700.

[sfleuriet]

yeah i know the 3200 is going the speed of the 2700. so two 2700s added together, makes my 333mhz.

[shwaip]

yeah i know the 3200 is going the speed of the 2700. so two 2700s added together, makes my 333mhz.

One stick of PC2700 runs at DDR333.
Two sticks of PC2700 run at DDR333.
Three sticks of PC2700 run at DDR333.
Four sticks of PC2700 run at DDR333.
Five sticks of PC2700 run at DDR333.
Six sticks of PC2700 run at DDR333.
Seven sticks of PC2700 run at DDR333.
Eight sticks of PC2700 run at DDR333.

Frequency has nothing to do with number of sticks.

Think of your cpu and memory as two buckets of water (data) with a pipe between them. Adding more memory just makes the memory "bucket" larger. Increasing the frequency of the bus (going from DDR333 to DDR400) is like making the pipe bigger.

[sfleuriet]

ok