A64 Overclocking Guide

[zOaib]

The thing is that in K8 architecture memory receives it's frequency from the memory controller not the source clock.

Plus the fact that ratios don't explain all memory frequencys.

largo can u put it in more simple words , or examples .............. like what would be a step or steps to take in series to go from a 2.4ghz to above , thx ,

 

[breakfromyou]

so exactly what is the formula? to find out what your memory would run, say if you used a memory divider, with a 10.5 cpu multiplier?

half multipliers confuse me. dram clock usually jumps down a bit.

 

[sinner33]

The multiplier when it is 10.5, rounds the memory down to if the multiplier was 10. For memory, there is no such thing as half a multiplier. That is just something you can do on your motherboard =P Ex: 9.5=9,10.5=10, 11.5=11.

 

[trog100]

u would find your memory max by lowering the cpu multiplyer to slow it down then upping the external clock to speed your memory up.. this will also speed your cpu up but the memory should reach its max out point first..

example.. cpu multiplyer should be 11.. dropping it to 9 would lower the cpu speed by 2 x external clock.. the memory speed would still be at 1 x 1 external clock.. 200/400.. as u take up the external clock both memory and cpu go up with it.. but being as the cpu started off 400mhz less than its default it has plenty of room left to go up in speed.. your memory dosnt so it should bomb out first..

trog

 

[zOaib]

u would find your memory max by lowering the cpu multiplyer to slow it down then upping the external clock to speed your memory up.. this will also speed your cpu up but the memory should reach its max out point first..

example.. cpu multiplyer should be 11.. dropping it to 9 would lower the cpu speed by 2 x external clock.. the memory speed would still be at 1 x 1 external clock.. 200/400.. as u take up the external clock both memory and cpu go up with it.. but being as the cpu started off 400mhz less than its default it has plenty of room left to go up in speed.. your memory dosnt so it should bomb out first..

trog

that makes sense !

so how do i raise my memory after putting down my cpu say 400mhz from a 2.4 to a 2.2 ?

WHAT do i do next to increase the mem , is it the timing u r talking about or the mhz ?

 

[cmberry20]

DRAM ratios work that way on AXP and Intel platforms but A64 is another animal...

No, they also work with A64s as well. Not all motherboards (BIOS's) are the same so the guide is just a guide & is meant as an example. I own a MSI Neo 2 Plat Skt939 AGP & the ram dividers work just like I quoted. If i set my RAM speed to 166 & the HTT is at 200 the memory works at a ratio of 6/5 to the CPU FSB/HTT so my RAM is running at 166Mhz. Therefore if i set my HTT to 250 i get a a RAM frequency of 208Mhz.
I'm not saying you are wrong but i think your BIOS works differently to mine.

HTT itself has *nothing* to do with ram frequency on AMD K8-series.
Memory frequency on K8 is derived directly from cpu frequency.

Again not true - see above. But your statement contradicts itself. How can the ram frequency NOT be connected to the HTT when the HTT governs the cpu frequency. If you raise the HTT you raise the cpu frequency thus raising the ram frequency - do you see!!

 

[zOaib]

now i am definately confused !

 

[cmberry20]

i'm going to look at clearing the memory divider business up. It is a little confusing plus my motherboard (NForce3) may be different to common ones (NForce4)

 

[zOaib]

i'm going to look at clearing the memory divider business up. It is a little confusing plus my motherboard (NForce3) may be different to common ones (NForce4)

if u can fidn a good standardised explanation for how to go about overclocking , that would help a lot of us low level brains here ! thx

 

[largon]

cmberry20,

Ok. 208MHz with source clock 250MHz and divider "5/6" (166).

What happens if we drop to 9x250?

Huh? Memory frequency dropped from 208MHz to 205MHz?

Glitch? Well, let's try 8x250...

Now it went down to 200MHz?

What's going on? Why memory frequency is not 208MHz like it should be with divider 5/6? And WHY does the frequency decrease if multiplier is lowered?



This is why:

DRAM ratios work that way on AXP and Intel platforms but A64 is another animal...

HTT itself has *nothing* to do with ram frequency on AMD K8-series.
Memory frequency on K8 is derived directly from cpu frequency.

DRAM Clock = CPU Clock / Ceil(Memory Divider*)
Ceil(x) returns the smallest integer value ≥ to the original value.

*Memory dividers:
Divider "250" = CPU multiplier - 3
Divider "233" = CPU multiplier - 2
Divider "216" = CPU multiplier - 1
Divider "200" = CPU multiplier
Divider "183" = CPU multiplier + 1
Divider "166" = CPU multiplier + 2
Divider "150" = CPU multiplier + 3
Divider "140" = CPU multiplier + 4
etc.

->

Divider "166" = CPU multiplier + 2

1st pic:
10 * 250.52 = 2505.2
2505.2 /12 = 208.77 = 208.8

2nd pic:
9 * 250.52 = 2254.68
2254.68 /11 = 204.97 = 205.0

3rd pic:
8 * 250.52 = 2004.16
2004.16 /10 = 200.42 = 200.4

□

 

[trog100]

i think different mobos call things by different names and have different ways of alterings things.. i cant do a screen shot of my bios screen.. else i would..

try wadeing thru this link.. he he

http://forum.overclockersonline.com...74&start=0&S=0bd708b11e5a7d833e52e0164ef89a4b


trog

 

[cmberry20]

Largon, I see what you've done about the HTT not being related to the memory frequency. While this is completely true in your example & I'm not disagreeing with this method but my guide was written with the fact that the CPU multiplier is remaining the same when overclocking thus the HTT & dividers would only be responable for the memory frequency altering.

I'm in no way trying to prove yourself or anybody wrong, feedback is always welcome & will be updating the guide & memory dividers information later this month. Thanks.

 

[largon]

I'm not disagreeing with this method but my guide was written with the fact that the CPU multiplier is remaining the same when overclocking thus the HTT & dividers would only be responable for the memory frequency altering.

Let's compare ratio method and err... "my" method but this time cpu multiplier stays the same:

8 * 237.7 = 1901.2
1901.2 / 11 = 172.8
Ratio method:
237.7 * (3/4) = 178.28 - wrong

8 * 275.5 = 2203.9
2203.9 / 11 = 200.4
Ratio method:
275.5 * (3/4) = 206.6 - wrong

8 * 280.04 = 2240.04
2240.3 / 11 = 203.7
Ratio method:
280.04 * (3/4) = 210.0 - wrong

Ratio method gives wrong frequency with every multiplier other than 10.

 

[cmberry20]

Thanks Largon, will be updating my guide to show correct memory divider calculation.