AMD Athlon II (Propus/Rana) choppy 3D using *certain* overclocked configs

Big.Wayne

Big.Wayne

Big.Wayne

Soldato
Joined
11 Sep 2003
Posts
14,716
Location
London
Hello OcUK forum overclocking *headz*

I've been evaluating one of the newer AMD budget triple cores processors for just over a month and have bumbled into an interesting situation with *certain* overclocked configs causing a choppy 3D/gaming experience that I am currently unable to explain?

As I'm sure most of you are aware that unlike the Phenom II Black-Edition chips the Athlon II chips have a upwards-locked CPU multi so overclocking needs to be performed by adjusting the HT ref. Clock, as all the other buses are linked to this base frequency it is necessary to utilize a number of dividers to keep the whole shebang running stable and roughly in spec . . .

The issue I am posting about is when using certain overclocked configs the 3D performance takes quite a hit, games get unexpected lags and benchmarks such as 3DMark become choppy (skipping/pausing) etc . .

I have to state straight away this problem does not exist at stock speeds or in certain overclocked configs so I don't want to send out the wrong message here but I think there is some unknown ratio that needs to be maintained when balancing the various buses in order that the hardware communicates correctly with all relevant subsystem . . .

I'm throwing this out there in the hope some gifted trouble-shooter/engineer can help me solve the *puzzle* :)

System Spec:



  • Athlon II X3 425
  • ASUS M4A785D-M Pro (Bios #0506)
  • Kingston Hyper-X DDR2 1066 (2x2GB)
  • Sapphire HD 4870 512MB (cat 9.11/9.12)
  • Corsair HX520W PSU
  • ThermoLab Baram Passive Cooler
  • Windows XP Pro 32-bit

Config #1 (below): Prime Stable and *silky smooth* in 3D . . .

3375mhzblend01.gif


Config #2 (below): Prime Stable but *choppy* in 3D . . .

3250mhzblend01.gif


Config #3 (below): Prime Stable but *choppy* in 3D . . .

3325mhzblend01.gif


I have been running the first config (#1) all over the xmas period with zero issues but am now trying to get my chip up to 3.5GHz/3.6GHz but can't do that until I learn about the correct ratio between all the different buses?

My thoughts are that while using certain configs I am creating a bottleneck somewhere that is causing a 3D-Problem but so far its not obvious what it is. I am slowly using a combination of trial and error to work this out but hopefully someone out there may see something that I am missing . . . I will be adding a fan to the CPU cooler just in case this is heat related but I think the issue lay elsewhere . . .

As already mentioned the 3D performance in the correct configs is great with a single HD 4870 so I don't want this issue to be misconstrued but I suspect other people using similar hardware may run into this also so this really needs to be solved . . .

Thanks in advance for any insights! :cool:
 
Last edited:
I would guess its NB Frequency and the ratio that you are running between CPU / NB Frequency.. Following my other reply from memory you need to keep the NB between 1000 - 1200 mhz less than the CPU Frequency for optimum performance.
 
Last edited:
buttkinz said:
http://www.overclockers.com/forums/showthread.php?t=596023

this thread tackles the frequencies aimed for on the NB and HTT bus, I'v been following this and have managed 3.7-3.8ghz ok but I cant seem to get past the choppyness and low fps, especially in crysis. hope the link helps, its got a few graphs on his testing. in the mean time il try out your config #1 and see if it helps :)

cheers!
Click to expand...

That was the tread I was looking for :)
 
I will put together a graph based on the forumla and then we can start to add in known 'stable' values for the NB Frequency at set CPU Frequencies.. Also I think we should split these based on CPU type.. so maybe PII, Athlons, etc..should make a nice overclocking resource
 
good idea mate, one thing to note, some chips have the 13.5x multiplier like waynes, mine has the 13x so maybe the correct settings will be different.
 
+1 for the NB/HTT issues. I cant explain it with complete technical accuracy, but i've been told that if the speeds of the cpu and nb/ht differ by too much or too little you get the choppyness you've been seeing as one component is waiting for the other. They sort of become slightly unsynchronised so to speak. The only other thing would be unstable memory, every now and then this isnt picked up by prime (unless you've done a blend), so perhaps run memtest and see if everything is ok on that front.
 
Last edited:
the cpu-nb frequency needs to be 3x the amount of the ram speed.

In general the CPU NB clock should be at least three times the Memory clock
(example in case of DDR3-1600: 3 x 800MHz = 2400MHz NB clock)
Click to expand...

also higher HTT helps in 3d apps
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom