RAM Divider. Overclocking.

NachT · 11 Nov 2006 at 21:21

Hi there,

I'm new to all this overclocking stuffs, just thought i'd ask a few Q's.

I'm wanting to basically run my setup faster... obviosly

So, is it right that you get a much higher preformance boost by upping the FSB rather than the clock speed?

Currently i'm running: AMD 4800. PC4000 Ballistix RAM.

FSB is 200 mhz on the CPU, and it was 200 mhz on the RAM. But i've changed the RAM divider? I think.. lol, to 250. So now my RAM is at 240mhz and the CPU is at 200 mhz. Should I not be using the divider and just clocking the overall FSB "properly" ?

I'm also wanting to lower my RAM timings, would the best way to do this just be lower by 1 digit, load windows, it's working, lower it again?

/NachT

mikeymike · 11 Nov 2006 at 21:26

you wuna set the divider to 1:1 then push the actual FSB up in increments of 5mhz until you lose stability or tempts get too high, you will probably also want to drop the htt multiplier from 5* to 4*

mikeymike · 11 Nov 2006 at 21:28

regarding your ram, you will have one of the two version of ballistix 4000, it will either do 250mhz @ 2.5-2-2-8 or 3-3-3-8, try setting the timings to 2.5-2-2-8 and see how far it will go before windows refuses to boot

NachT · 12 Nov 2006 at 17:02

mikeymike said:
you wuna set the divider to 1:1 then push the actual FSB up in increments of 5mhz until you lose stability or tempts get too high, you will probably also want to drop the htt multiplier from 5* to 4*

Thanks mate, i'll try to try that.

Btw is this the divider option?

If it is, how do I set it to 1:1 :rolleyes:

Yeah i'm new to this, as you can totaly tell

Nutbusta · 12 Nov 2006 at 17:04

To set it to 1:1, just set it to 200MHz mate

If your overclock becomes unstable then drop it to 166 and see if that solves the prob. If it does then you know it was the ram hitting the wall not the CPU or mobo

Ronaldo · 12 Nov 2006 at 19:15

just wondering, i though amd 64 dont run 1:1 as in its always on divider because of HTT

Nutbusta · 12 Nov 2006 at 19:27

Ronaldo said:
just wondering, i though amd 64 dont run 1:1 as in its always on divider because of HTT

Well, kinda, perhaps.

S939 by default divide the HTT speed of 1000MHz by 5 to get the stock ram of 200MHz.

This is considered 1:1

166 is 5/6 of 200 therefore 166 is a 5/6 divider.

therefore if you oc the FSB to 250 and run the ram on a 166 divider you'll be running the ram at approx 208MHz (5/6)

Of course you'll need to change the HTT multi to 4 because 250x4=1000 (in spec)

Also note that there's little point in oc'ing the htt. Keep it at 1000 approx.

Google A64MemFreq11.exe for a great little tool that will work this stuff out very acurately for you.

Hope this helps

NachT · 12 Nov 2006 at 20:06

Nutbusta said:
Well, kinda, perhaps.

S939 by default divide the HTT speed of 1000MHz by 5 to get the stock ram of 200MHz.

This is considered 1:1

166 is 5/6 of 200 therefore 166 is a 5/6 divider.

therefore if you oc the FSB to 250 and run the ram on a 166 divider you'll be running the ram at approx 208MHz (5/6)

Of course you'll need to change the HTT multi to 4 because 250x4=1000 (in spec)

Also note that there's little point in oc'ing the htt. Keep it at 1000 approx.

Google A64MemFreq11.exe for a great little tool that will work this stuff out very acurately for you.

Hope this helps

Thanks for all the info mate, it has helped.

I do have a question tho, why should I be putting my divider to 1:1 ? If I have it higher the RAM runs faster... I don't get why I should be lowering it

Nutbusta · 12 Nov 2006 at 20:20

If your ram runs faster then you should use that headroom to overclock the FSB and CPU.

On A64 machines you actually get a big drop in prformance if you run your ram higher than the divider of the HTT (or higher than the fsb)

If you ram does not run faster than 200 then you can use a 166 divider to allow you to overclock by about 22% and keep the ram at 200MHz

So on my Sempron machine that gives me:

200/5*6=240

240*8=1920MHz and I'd still have my ram at 200MHz

(stock speed 1600MHz)

NachT · 12 Nov 2006 at 20:30

Being new it all sounds so complicated lol, i'll get used to it though.

Thanks for your help, i'll have a go at messing around with some settings and see what happens heh.

Insanity · 12 Nov 2006 at 20:41

It sounds complicated, but its not. There's a few things you need to remember:

- Lower HT Multiplier to 4x (explained later on)
- Higher CPU FSB = Higher overclock
- Raising the CPU FSB also raises the ram speed
- From my own experience, ram doesnt like to clock as much as a CPU
- Setting the initial Ram speed lower than stock (eg: DDR400 down to DDR333) will give you extra headroom for clocking the CPU, remembering that the ram speed will increase when you increase the FSB for your CPU, so adding 40 - 50mhz to the CPU FSB will bring your ram speed back up to stock, or very close to it.

And lastly, the HT Link (as shown in the newest CPU-Z), which should always be close to 1000Mhz.

An easy way to calculate this is eg: 250(FSB) x 4(HT multi) = 1000. If you were to increase your FSB to the cpu anymore than 250mhz, you would need to drop the HT Multiplier down to 3x. Im not entirely sure why the HT Link isnt supposed to be higher than 1000, but thats what i've been told so thats what i went with.

Nutbusta · 12 Nov 2006 at 21:17

Insanity said:
It sounds complicated, but its not. There's a few things you need to remember:

- Lower HT Multiplier to 4x (explained later on)
- Higher CPU FSB = Higher overclock
- Raising the CPU FSB also raises the ram speed
- From my own experience, ram doesnt like to clock as much as a CPU
- Setting the initial Ram speed lower than stock (eg: DDR400 down to DDR333) will give you extra headroom for clocking the CPU, remembering that the ram speed will increase when you increase the FSB for your CPU, so adding 40 - 50mhz to the CPU FSB will bring your ram speed back up to stock, or very close to it.

And lastly, the HT Link (as shown in the newest CPU-Z), which should always be close to 1000Mhz.

An easy way to calculate this is eg: 250(FSB) x 4(HT multi) = 1000. If you were to increase your FSB to the cpu anymore than 250mhz, you would need to drop the HT Multiplier down to 3x. Im not entirely sure why the HT Link isnt supposed to be higher than 1000, but thats what i've been told so thats what i went with.

What he said.

I was doing well with the numbers but Insanity has explained it better.

HTT should be left around 1000 because it doesn't overclock all that well and at stock speed it has soooo much bandwidth to play with.

Imagine the M25 with 50 lanes. Then if you imagine adding 2 more it wouldn't make the blindest bit of differance because everyone has plenty of road anyway

NachT · 12 Nov 2006 at 22:08

Insanity said:
It sounds complicated, but its not. There's a few things you need to remember:

- Lower HT Multiplier to 4x (explained later on)
- Higher CPU FSB = Higher overclock
- Raising the CPU FSB also raises the ram speed
- From my own experience, ram doesnt like to clock as much as a CPU
- Setting the initial Ram speed lower than stock (eg: DDR400 down to DDR333) will give you extra headroom for clocking the CPU, remembering that the ram speed will increase when you increase the FSB for your CPU, so adding 40 - 50mhz to the CPU FSB will bring your ram speed back up to stock, or very close to it.

And lastly, the HT Link (as shown in the newest CPU-Z), which should always be close to 1000Mhz.

An easy way to calculate this is eg: 250(FSB) x 4(HT multi) = 1000. If you were to increase your FSB to the cpu anymore than 250mhz, you would need to drop the HT Multiplier down to 3x. Im not entirely sure why the HT Link isnt supposed to be higher than 1000, but thats what i've been told so thats what i went with.

Oh thanks, now I did understand that a bit better

I take it the HT link, HTT, HT Multiplier are all the same thing, and the HT stands for hiper transport?

Out of intrest, what FSB do you think I could reach on an S939? or is there more to it? e.i. what mobo / RAM / PSU I have effects what I can do aswell?

Insanity · 12 Nov 2006 at 22:31

NachT said:
Oh thanks, now I did understand that a bit better

I take it the HT link, HTT, HT Multiplier are all the same thing, and the HT stands for hiper transport?

Out of intrest, what FSB do you think I could reach on an S939? or is there more to it? e.i. what mobo / RAM / PSU I have effects what I can do aswell?

HT Link = Bandwidth (i think)
HTT = FSB
HT Multiplier = Err... the Multiplier that works with the FSB to come up with the HT Link speed/bandwidth/whatever you want to call it.

HTT (or FSB) x HT Multiplier = HT Link

So they are all different entities.

Your max FSB (or HTT) will be limited by what your chip can handle, whether you use a divider for the ram (underclocking the ram for headroom) aswell as if your ram likes to overclock, and what your motherboard can handle. It's pretty much hit and miss, there's no magical numbers.

Your PSU will only really affect it if it has unstable rails as far as i know.