What's Wrong With This?

Agis · Oct 25, 2008

Hi guys,

Can you please tell me what's wrong with the following combination.

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I have CPU speed 3555MHz,Multi 15,Divider 1/2.

If the formula "CPU Speed / ceiling ((Multi / Divider) / 2) is correct then....

3555 / ceiling ((15 /0.5) / 2)=3555 / (30 / 2)=3555 / 15= 237Mhz DDR2 474Ram speed.

Why CPU-Z detects 474 Mhz?What am i doing wrong?

Thanks a lot.

Agis

QuietIce · Oct 25, 2008

It looks like your RAM divider is set at 1:1 (DDR2-800). It's been awhile since I've played with my Phenom but, IIRC, 1:2 is typically shown for a RAM limit of 800 on those chips. If you use 1:1 (1.0) as the RAM divider in your equations you'll get 474 MHz or DDR2-948.

Your SuperPi times seem to verify that - they're almost exactly what mine are when scaled up (I calculated 21.68s) to those speeds, which are really great BTW!

What board do you have ...?

jonspd · Oct 25, 2008

237x2 = 474 right?

1:2 = bus x 2 = ram freq

Agis · Oct 26, 2008

QuietIce said:
What board do you have ...?

This is a system i build for a friend,the board is an Asus M3A79-T Deluxe and i am worry because he is getting strange readings from CPU-Z.

So you think is a CPU-Z problem?We will get another version to try.

I thought i got wrong the way to calculate Ram speed

jonspd said:
237x2 = 474 right?

1:2 = bus x 2 = ram freq

I don't think this is the correct way to calculate ram speed

if for example...

1:1 =bus x 1 = what ram freq? 237 x 1= 237Mhz?

Thanks a lot guys.

Agis

QuietIce · Oct 26, 2008

Agis said:
This is a system i build for a friend,the board is an Asus M3A79-T Deluxe and i am worry because he is getting strange readings from CPU-Z.

So you think is a CPU-Z problem?We will get another version to try.

I thought i got wrong the way to calculate Ram speed

Your calculations are correct except for the divider. On that board a limit of 800 should give a 1:2 reading in CPU-Z.

I know it's confusing but that is the actual RAM bus frequency. The other number is the DDR2 "rating" because DDR2 has two transfers per cycle ...

Agis · Oct 26, 2008

QuietIce said:
On that board a limit of 800 should give a 1:2 reading in CPU-Z.

I know it's confusing but that is the actual RAM bus frequency. The other number is the DDR2 "rating" because DDR2 has two transfers per cycle ...

There is something i am missing here,if a limit of 800 gives a 1:2 divider what divider should i use in the calculation to get the correct result?

How the calculation should be done?

Agis

QuietIce · Oct 26, 2008

A limit of 800 shows a 1:2 divider in CPU-Z. But an 800 limit is still 1:1 regardless of what CPU-Z is showing (800/800 = 1.00). If the board had a top setting of 533 instead of 1067 then a 400 setting would be 1:1 - it all depends on the way the BIOS is labeled.

I'll look into it a little farther but I think we're really back to the old rules - slightly changed to 2*bus*(RAM Setting/800) ...

Agis · Oct 26, 2008

QuietIce said:
If the board had a top setting of 533 instead of 1067 then a 400 setting would be 1:1 - it all depends on the way the BIOS is labeled.

I'll look into it a little farther but I think we're really back to the old rules - slightly changed to 2*bus*(RAM Setting/800) ...

I think the problem is that they use a 200 stock FSB for the CPUs instead of 400,this is more of a ram multiplier then divider.

I saw your thread sometime ago and i thought that everything was easy

http://www.ocforums.com/showthread.php?p=5567166

Where is the AM2+ and AM3 guide?

Well...it took me some time to learn how to calculate always correctly the A64 and i thought that AM2+ systems will be the same,now the only thing missing is Intel's IMC to be at total loss

If you find a way that this thing works please let me know.

Agis

jonspd · Oct 26, 2008

there is no FSB on am2+

its a ht ref which is 1:2 for ram unless set to 1:1.

Agis · Oct 30, 2008

jonspd said:
237x2 = 474 right?

1:2 = bus x 2 = ram freq

I think you were correct.The way to calculate ram speed on K10 has nothing to do with A64,it's just like Intel's.

From what i found and if i understood correct to calculate ram speed you need to multiply FSB by ram multiplier.

Multiplier 200 is 1:1, 266 is 1:1.33, 333 is 1:1.67, 400 is 1:2, 533 is 1:2.66.

So at FSB 237 the possible ram speeds i can get are:

237 x 2.66 =DDR2 1261
237 x 2 = 474 =DDR2 948
237 x 1.67 = 396 =DDR2 792
237 x 1.33 =315 =DDR2 630
237 x 1 = 237 =DDR2 474

I don't know if my English are good enough to explain this correct.

Thanks a lot for the help guys

Agis

jonspd · Oct 30, 2008

that is correct.

m4xwellmurd3r · Oct 30, 2008

here's a way of looking at the ratios
for every 1mhz on the fsb, you get 1mhz on your ram or 1:1
in his case, for every 1mhz on the fsb, he gets 2 mhz on the ram, or 1:2 and so on.
so instead of "dividers" they are now "ratios"
before it used to be CPU/RAM but now it's FSB:RAM

QuietIce · Oct 31, 2008

Agis said:
I think the problem is that they use a 200 stock FSB for the CPUs instead of 400,this is more of a ram multiplier then divider.

I saw your thread sometime ago and i thought that everything was easy

http://www.ocforums.com/showthread.php?p=5567166

Where is the AM2+ and AM3 guide?

Well...it took me some time to learn how to calculate always correctly the A64 and i thought that AM2+ systems will be the same,now the only thing missing is Intel's IMC to be at total loss

If you find a way that this thing works please let me know.

Agis

It's a simple matter for the equations to work properly.
All that need be done is skip the rounding step and use the correct ratio for your equations.
Regardless of what CPU-Z reads your setting of 800 is still a 1:1 ratio, not 1:2.

3555 ((15 /1.0) / 2)=3555 / (15 / 2)=3555 / 7.5=474Mhz or DDR2-948 RAM speed.

Agis · Oct 31, 2008

QuietIce said:
It's a simple matter for the equations to work properly.
All that need be done is skip the rounding step and use the correct ratio for your equations.
Regardless of what CPU-Z reads your setting of 800 is still a 1:1 ratio, not 1:2.

3555 ((15 /1.0) / 2)=3555 / (15 / 2)=3555 / 7.5=474Mhz or DDR2-948 RAM speed.

Yeah,it works this way also.

A guy in AMD forums told me a third way is well:

Current FSB / Default FSB X Ram speed set in Bios= Ram speed

i.e. (237/200) X 800 =1.185 X 800 = DDR2 948

Seems there are more than one ways to calculate ram speed in AM2+ systems.

Thank you very much.

Agis

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