Problems with the x2 AMD's ???

[cooljimy84]

ok just bought a 5200+ amd dual core.

but ran across this on the net !!

http://www.anandtech.com/cpuchipsets/showdoc.aspx?i=2762&p=10

Tis not clear to me if this will affect my chip.

lol

Cheers guys and girls

 

[Tetras]

If it still works like that then yes, the 5200+ has the same multiplier (13), just 1MB per cache per core instead of 512KB in the 5000+.

 

[Jokester]

I think the issue he's referring to is the half multiplier issue, because currently motherboards don't actually support them. Just means that instead of 12.5 or whatever it will run at 12. Easy enough to clock up to make up the difference and more.

I think you only get the half multipliers on the new 65nm chips and I don't think there's any of them floating about yet available to the general public.

Jokester

 

[cooljimy84]

Kool, so i'll just have to make up the speed with a faster "fsb" , like i need a reason to start overclocking !!!

Cheers guys and girls

 

[Jokester]

Nah, your's doesn't have the half multiplier, it only effects the 65nm chips, which your one isn't.

Jokester

 

[Tetras]

It is the way that the Athlon 64/X2 chips calculate the memory clock speed that is responsible.

The formula they use is CPU frequency / an internal memory divider (based on either the CPU multiplier or an FSB/mem divider ratio but can't be directly manipulated) and because of that it causes a few problems since the controller can't use half multipliers.

On 939 it would be:
13 (CPU multi) x 200 (HTT) = 2600

2600 / 13 = 200 (PC3200).

On AM2 it can't find a multiplier to use to hit 800 Mhz cos it is limited to integers:

2600MHz CPU Frequency / 6 = 433MHz DDR2-866 Memory Frequency

2600MHz CPU Frequency / 7 = 371MHz DDR2-742 Memory Frequency

The clock speed of the processor is unaffected, since that uses the traditional FSB x multiplier to calculate the clock speed, it is the memory frequency, that no longer uses the FSB (like other chips do).

As Jokester mentioned you only need a little FSB clocking to "fix the issue", If you use a 215 FSB (2795 Mhz CPU) you can get 399 Mhz (798 DDR).

 

[Jokester]

I'm thinking of the wrong thing, yeah it's the way AMD works out the memory dividiers, instead of running it directly off the FSB, it works them out by taking the CPU speed into account as well, which results in a rounding error when the multiplier is odd.

Jokester