What is a memory divider

[MBrown]

I hear everyone talking about memory dividers, but I never was able to figure out what a memory divider is. So what is it? How do you use it?

 

[theMan]

normally the memory runs at the same speed as the FSB or HTT. with a divider, you can run it at a fraction of the speed. this allows you to have more flexibility in your overclock.

 

[MBrown]

ahh. Maybe I set the divider with out even knowing it. I am forcing my memory to run at 400mhz instead of going increasing with the cpu. If I lower that to maybe 333 to see if I can get more speed out of my processor is that going to degrade my performance quite a bit?

 

[Effect]

As they say, CPU is king. As long as your RAM (after o/c) runs close to 400mhz, it's all good.

 

[StrangerGuy]

A ratio of FSB clock to memory clock.

 

[MBrown]

Originally posted by: Effect
As they say, CPU is king. As long as your RAM (after o/c) runs close to 400mhz, it's all good.

From what I can see, I only have 4 speeds that I can manually run my ram at. 100, 133, 166, 200. Is there a place where there are more options than that or is that just on DFI Motherboards?

 

[CosmoHorizon]

Havn't used your board before, but my A8N32 doesn't like me running on manual speed mode, even though it is the same clock as what the board sets it on auto. Try that on DFI board, on my board the auto setting bumps my Kingston value ram to 213Mhz, which translates to 426Mhz. Not too bad for a value ram, but latency is 3-3-3-8. Bank cycle 17clock and idle timer 16 clock.

Plenty of ppl here with DFI board, but with that said, it depends on your CPU HTT setting. Hopefully some1 will be able to help me tighten the loose timing on my RAM too!

 

[n7]

 

[MrX8503]

If you have pc3200 ram. Which is ddr 400mhz that ram can only run at a max of 400mhz stabley. But when you OC it increases the memory over 400mhz, so you run a divider so that the ram stays under or at 400mhz while your CPU goes even higher.

 

[theMan]

Originally posted by: MrX8503
If you have pc3200 ram. Which is ddr 400mhz that ram can only run at a max of 400mhz stabley. But when you OC it increases the memory over 400mhz, so you run a divider so that the ram stays under or at 400mhz while your CPU goes even higher.

yes, unless you overclock your ram, which is very easy to do, depending on the type. even pc3200 value ram i have running at 225mhz.

 

[sygyzy]

What is the performance hit for using the divider?

 

[robertk2012]

Originally posted by: sygyzy
What is the performance hit for using the divider?

none

 

[m3a2]

Originally posted by: robertk2012

Originally posted by: sygyzy
What is the performance hit for using the divider?

none

Unless your divider x your htt makes your ram run less than the normal speed of the ram

 

[CP5670]

Originally posted by: n7
No, you're misunderstanding what the divider does.

It doesn't lock the RAM's speed, it sets the fraction of the HTT speed that the RAM runs.

Normally RAM runs @ DDR400 (200), same as the HTT.

But setting the divider to 166 aka 333, you're setting the RAM to run at 5/6 of the speed of the HTT, or 0.833%.


For example, if you're using the 166 divider with your HTT @ 240, it would set your RAM to 200 MHz (DDR400), since 5/6 of 240 = 200.

It usually comes out a little less than that depending on the processor's multiplier. (you have to multiply the HTT speed by (CPU multiplier) / ceiling[(CPU multiplier) / (divider ratio)] instead of just the divider to get the exact memory speed)

 

[sygyzy]

Originally posted by: m3a2

Originally posted by: robertk2012

Originally posted by: sygyzy
What is the performance hit for using the divider?

none

Unless your divider x your htt makes your ram run less than the normal speed of the ram

Even I knew that!

 

[robertk2012]

Originally posted by: m3a2

Originally posted by: robertk2012

Originally posted by: sygyzy
What is the performance hit for using the divider?

none

Unless your divider x your htt makes your ram run less than the normal speed of the ram

lol well thats common sense. But it really wont make that much of a difference in that situation unless you are underclocking your ram a lot.

 

[n7]

Originally posted by: CP5670

Originally posted by: n7
No, you're misunderstanding what the divider does.

It doesn't lock the RAM's speed, it sets the fraction of the HTT speed that the RAM runs.

Normally RAM runs @ DDR400 (200), same as the HTT.

But setting the divider to 166 aka 333, you're setting the RAM to run at 5/6 of the speed of the HTT, or 0.833%.


For example, if you're using the 166 divider with your HTT @ 240, it would set your RAM to 200 MHz (DDR400), since 5/6 of 240 = 200.

It usually comes out a little less than that depending on the processor's multiplier. (you have to multiply the HTT speed by (CPU multiplier) / ceiling[(CPU multiplier) / (divider ratio)] instead of just the divider to get the exact memory speed)

Yes, thanx, you are right; i'm wrong.

I got so used to doing the math with 10x multi CPUs i tend to forget that way of calculating it isn't actually the right way for other multipliers, etc.

 

[5t3v0]

So many people get the formula wrong. Even my BIOS reports memory the frequency wrongly. To reiterate what CP5670 said with an example. My CPU overclock is 280 HTT x 9 = 2520MHz and my memory divider is 166 or DDR333 (5/6).

Memory Frequency = (HTT x CPU mutilplier) / CEIL(CPU multiplier x (Default HTT / Memory Divider))

= (280 x 9) / CEIL(9 X (200/166))

= 2520 / CEIL(10.84)

= 2520 / 11

= 229.09

CEIL = ceiling, which means round up to the nearest whole number

There's an Anandtech article explaining it more here.

The easiest way to calculate a new memory speed before embarking on an overclock is to use an excellent little app called A64MemFreq1.1

 

[KoolDrew]

From what I can see, I only have 4 speeds that I can manually run my ram at. 100, 133, 166, 200. Is there a place where there are more options than that or is that just on DFI Motherboards?

Most motherboards (including mine) only have those 4 memory dividers. However, I believe you can use A64Tweaker to set a different divider.

 

[5t3v0]

Originally posted by: KoolDrew

From what I can see, I only have 4 speeds that I can manually run my ram at. 100, 133, 166, 200. Is there a place where there are more options than that or is that just on DFI Motherboards?

Most motherboards (including mine) only have those 4 memory dividers. However, I believe you can use A64Tweaker to set a different divider.

You can but I found it to be well dodgy so gave up with it. It didnt seem to detect some timings correctly on my board (Tref I think was one of them) so applied the wrong setting & caused BSODs. I even tried older versions but they were no better. Unless mobo mfrs start releasing enhanced BIOSes, the only way to get more dividers reliably is to buy a DFI Lanparty board which is exactly what I intend to do.