Memory divider weirdness

[SonicIce]

My friend had an Athlon 64 3800+ Venice and MSI K8T Neo-F. We tried to OC it to 220*12 for 2640mhz. we used 183 memory divider which should mean that 220*0.9 equals 198mhz memory. (oc guide) But why does cpu-z say the memory is running at 188? it says the FSBRAM ratio is CPU/14. Where does it get that from?

 

[n7]

That's because you have to round up if not an exact number when calculating dividers for AMD.

12x200 = 2400
2400 / 183.33* = 13.09 rounded up to 14.

12x220 = 2640
2640 / 14 = 188.571etc aka DDR-377.


If your RAM can do it, try 11x240 with the 183.33* divider, that should be 220 (DDR-440).

 

[SonicIce]

Ok thanks I get why I was wrong. What do you mean by if not an exact number? Why does Zebo's guide say to just multiply FSB by some decimal?

 

[n7]

His guide is excellent, but also incorrect when it comes to calculating dividers.

Note this line:

Originally posted by: Zebo
This is the rough way to calculate IE close enough..

It's not actually close enough IMO, as you will sometimes find the numbers calculated that way aren't at all the same as reality.

There's another way to do the calulations; i just forget how.
I've always remembered to do them the way i mentioned, which works just fine.

What i mean by exact numbers is that is needs to be 12.00 or 13.00 or 14.00, etc.

Example.

11x200 = 200.
Say we're using the 166.66* divider.

That's 2200 / 166.66* = 13.2 which you must round up to 14, not 13.

Or for your case, it's 12x200 = 2400 / 183.33 = 13.0909* which you must round up to 14.
Then 12x220 (2640) / 14 = 188.57

 

[SonicIce]

ohh ok. thanks alot man. :beer: you rule