ZEBO - great looking guide for A64

[996GT2]

 

[Neos]

Originally posted by: jgigz

Originally posted by: 996GT2

Originally posted by: Neos
Zen - took your advice and bumped the CPU voltage to 1.45 and I am at 270. Pretty kewl!

Ok, guys. If I am supposed to get a 1:1 ratio using the Memclock and CPU Freq. then why do I get this?
CPU - 255 / Mem (per CPUZ) - 131.5 (Memclock set to Auto)
CPU - 270 / Mem (Per CPUZ) - 134.5 (Memclock - Auto)

With a HIGHER CPU freq. - should not the memory go LOWER to maintain a 1:1?

When you set a memory divider, it's set assuming 200 HTT. That is, if you have a 1:1 divider, both FSB and RAM run at 200 MHz. If you have a 1:2 divider, FSB runs at 200 while RAM runs at 100 MHz. Now, factor in the overclocking. When you overclock your HTT, the memory speed must INCREASE to maintain that same ratio. i.e. 1:1 ratio, when your HTT is at 225 your RAM must also work at 225; 1:2 ratio when your HTT is at 250 your RAM must be at 125, etc.

Damn you're good you quoted someone else and answered a few of my questions

Yes, he is good - but I am going to have to study some more to understand whats up. Since this is all in Auto (ceptin the CPU multi) then to maintain a 1:1 - would not this be the case?
When the CPU goes up - the the memory goes down.
When the CPU goes down - the memory goes up.

Don't fuss at me if I am way off base. Sometimes I can be a little thick.

 

[996GT2]

Well to answer you let's use some examples:

Let's pretend you have a 1:1 ratio. With that ratio, the RAM ALWAYS runs at the SAME speed as the FSB (or in AMD's case, the HTT)

You have a stock 200 HTT. Your RAM is running at 200 MHz (DDR400). Everyone is happy.
When you increase HTT to say, 225, your RAM speed has to keep the 1:1 ratio. That is, it must still run at the SAME speed as the HTT. So it must INCREASE its clock to 225 mhz, along with the CPU's HTT.

Now let's use a 3:4 multiplier as another example.
When you have a stock 200 HTT with the 3:4, your RAM and HTT are running in a locked 3:4 ratio. That is, for every 4 MHz of the HTT, the RAM speed increases by 3 MHz. so at 200 HTT the RAM speed would be 150 MHz.

Now let's say you overclock a bit and raise your HTT to 265. The memory cannot stay at 150 MHz because that would not keep the 3:4 ratio. It must also increase its speed, in this case to nearly 199 MHz.

This is if you use FIXED dividers. When you set it to "Auto", I think your board chooses the most appropriate divider for the HTT speed and modulates RAM speeds automatically. I could be wrong here though.


For more info read this guide:
http://forums.extremeoverclocking.com/showthread.php?t=149717

 

[zendari]

Originally posted by: Neos

Originally posted by: jgigz

Originally posted by: 996GT2

Originally posted by: Neos
Zen - took your advice and bumped the CPU voltage to 1.45 and I am at 270. Pretty kewl!

Ok, guys. If I am supposed to get a 1:1 ratio using the Memclock and CPU Freq. then why do I get this?
CPU - 255 / Mem (per CPUZ) - 131.5 (Memclock set to Auto)
CPU - 270 / Mem (Per CPUZ) - 134.5 (Memclock - Auto)

With a HIGHER CPU freq. - should not the memory go LOWER to maintain a 1:1?

When you set a memory divider, it's set assuming 200 HTT. That is, if you have a 1:1 divider, both FSB and RAM run at 200 MHz. If you have a 1:2 divider, FSB runs at 200 while RAM runs at 100 MHz. Now, factor in the overclocking. When you overclock your HTT, the memory speed must INCREASE to maintain that same ratio. i.e. 1:1 ratio, when your HTT is at 225 your RAM must also work at 225; 1:2 ratio when your HTT is at 250 your RAM must be at 125, etc.

Damn you're good you quoted someone else and answered a few of my questions

Yes, he is good - but I am going to have to study some more to understand whats up. Since this is all in Auto (ceptin the CPU multi) then to maintain a 1:1 - would not this be the case?
When the CPU goes up - the the memory goes down.
When the CPU goes down - the memory goes up.

Don't fuss at me if I am way off base. Sometimes I can be a little thick.

No, they are directly proportional. Not inverses.

The term divider, for all the ratios refers to memclock/200. With memclock at 200, you obviously get 1:1. With memclock at 100, you get 1:2.

The ratio gives you memory speed:FSB. So the formula

memory speed = memclock*FSB/200

is used. The setting "auto" simply chooses a number to put into the memclock (how it does that I'm not sure). In your example, we know FSB and we know memory speed thru CPU-Z, and thus can figure out memclock that "auto" is setting.

You have 200 mhz ram, so when you are done you want to keep memory speed around the 200 mark. So, as you increase FSB, memclock has to decrease.

 

[Neos]

OK. I am just glad it works as well as it does in Auto.

Thanks for all the input, Guys. Got me on the right track.