Bus vs. Multiplyer - Which is better to OC?

[Kramerica]

I could up the multiplyer settings and underclock my bus, or i could decrease the multiplyer settings and increase my bus, and I would get the same speed; correct? Thus, what is the point of increasing your system bus beyond normal parameters. Does OCing the bus and multiplyer settings decrease the temp. of the cpu, or create any difference in the stability/performance of the PC (as opposed to simply increasing the multiplyer settings more)? I need input here, b/c I don't know which way is the better way to overclock. Thanks

[oc jason]

BUS by far is MUCH better-10x100=1000, and 7.5x133=1000 same right-WRONG. All the other parts of your computer run at a fraction of the BUS, say your video card is 1/4 divisor of the BUS so if you are at 10x100=1000 then the video card is 1/4 of the BUS which would put the video card at 25 mhz, but if you are at 7.5x133=1000 with the videocard at 1/4, it would now be running at 33.25mhz-instead of 25. And your still at 1000mhz overall-same speed better performance. So goes for all the other things in the comp =soundcard/HD/Videocard/NIC all runs faster with a higher BUS

AGP(video)=1/4
sound=1/3
nic=1/3
etc.etc

[!-=sky=-!]

above post is true but in my opinion they give the same results b/c when i try it with my duron 750 it just gives 1 or 2 points higher in the cpu benchmark in sisoft sandra when i oc with fsb then in multiplier

[!-=sky=-!]

sorry double post

[Flanagun]

You donit want to go too far with the bus speed. Running your hardware on too high a bus will sometimes lead to problems with the PCI bus or your ram.

[cntw82oc]

what i have found is that if you're looking for just a few mhz (meaning you're debating between something like 11*108 and 11.5*103) then you would want to go with the higher fsb.......however, if you're looking at a big jump (something like 11.5 *103 vs 9 *135) then it really doesnt make much of a difference. The reason being is that when you're using a fsb speed under 133 the divider is usually set at 1/3 ie. fsb = 103, pci bus = 34. But when the fsb jumps over 133 the divider jumps to 1/4..
ie. fsb = 135, pci bus = 34.

Therefore, the pci bus in both scenarios (11.5*103 vs. 9*135) is going to be 34.



*head explodes*

someone correct me if i'm wrong...but this is what i've found.

[Kramerica]

thanks for the geed back guys :)

[ken257]

You want to get the fsb as high as you can and still be stable. Run memory tests in Sandra and you will see a big change, also 3DMark 2000 responds bigtime to the increased memory speed.

It is a balancing act you have to play with the multipier and fsb, keeping the fsb as high as possible to run at the desired speed.

[PDL]

cntw82oc is correct about the change in PCI speed once you hit 133.
In the manual for my A7V, the PCI speed at the default of 100 is 33.57. It goes up from there until you get to 133, then the PCI goes back to 33.33!
Oh if only it would go that high!!!

Duron700@1016(107x9.5)HSFonNorthbridg
Better memory on the way!!

[pqt]

For some reason, my Tbird 1.2 doesn't like multiplier 11x. If I set it @ 10.5x135 fsb it is rock stable. But @ 11x133, it won't even boot into windows !!

[TranceBear]

pqt (May 29, 2001 09:52 p.m.):
For some reason, my Tbird 1.2 doesn't like multiplier 11x. If I set it @ 10.5x135 fsb it is rock stable. But @ 11x133, it won't even boot into windows !!
What type of RAM are you using to get 135mhz? I seem to not be able to get over 133mhz. I can run 11x133 all day, but the second I go to 134mhz, all is not good, windows goes nuts. Damn I want 1.5ghz!!

[castle lager fan]

To get the best out of your system you will have to play with both the FSB and the multiplier. My suggestion is to tune down the multiplier first to below the CPU rating for speed. Then play with different bus speeds till you find the max of the system. As the sytem will become unstable and not the CPU. Make a note of this. Some motherboards offer more settings than others. I found the CAS on the memory one of the most significant factors on the FSB speed. If you can get memory that can do CAS latency of 2 at lets say 133 MHz. If you then set the CAS on the mobo to 2.5 you will be able to get much higher speed with your mem, in some benchmarks it may penalize you to have a high latency. Best is to buy mem that can do 150 MHz at 2 CAS.

Once you have the maximum FSB limit, you can calculate the various combinations of FSB speed your mobo gives you with different multiplier setting to give you the highest clock speed.

By bumping up the CPU core and FSB voltages you can get a bit more, BUT be careful as temps seem to skyrocket quickly. I currently can't get to 1.6 GHz without temp going wild and system getting unstable.

Hope this helps.

[asmodean]

That cas2.5 applies only to DDR.

[David]

FSB Ocing can be problematic. I got the FSB up t 112 @1.75volts and lost two partitions (4GB altogether) - not pretty

[wild_andy_c]

~(-=->sky<-=-)~ (May 29, 2001 10:03 a.m.):
above post is true but in my opinion they give the same results b/c when i try it with my duron 750 it just gives 1 or 2 points higher in the cpu benchmark in sisoft sandra when i oc with fsb then in multiplier

WRONG - the performance of a system cannot be judged by the CPU benchmark alone. A CPU benchmark will only tell you the internal capability of a CPU. At 10 x 100 or 7.5 x 133 this will be roughly the same. When you have to consider that the perfomance of a system relies on Memory bandwidth, CPU performance, bandwidth between Northbridge and CPU, bandwidth between northbridge and AGP, PCI bus speed etc - you realize that running the higher bus is much more important.

As for someone saying that running a high bus is dangerous to your peripherals - Yes it can be, but also it can be safe. What one must do before they attempt to do an overclock is firstly think about what they are doing. Do they really want to do 120Mhz FSB if they are gonna have to run their Hard disks at 40Mhz and what have you.

I have (from no known place - and I can't tell anyone) a GERMAN Duron proto that is running at 166Mhz FSB at 1328Mhz. Now - that is some performance I can tell you.

[oc jason]

nelly (May 30, 2001 04:22 a.m.):
FSB Ocing can be problematic. I got the FSB up t 112 @1.75volts and lost two partitions (4GB altogether) - not pretty

thats because you didnt have a chipset that could handle 133FSB once it is pushed too high then it can corrupt HD's if it was a kt133a chipset than the HD is the problem it cant handle high FSB

[oc jason]

Luv2Rave (May 29, 2001 10:45 p.m.):
pqt (May 29, 2001 09:52 p.m.):
For some reason, my Tbird 1.2 doesn't like multiplier 11x. If I set it @ 10.5x135 fsb it is rock stable. But @ 11x133, it won't even boot into windows !!
What type of RAM are you using to get 135mhz? I seem to not be able to get over 133mhz. I can run 11x133 all day, but the second I go to 134mhz, all is not good, windows goes nuts. Damn I want 1.5ghz!!

lower the multipier to 9 and i promise that your FSB will go up-its directly related multiplier~FSB lower/higher, higher/lower

[pqt]

Luv2Rave (May 29, 2001 10:45 p.m.):
pqt (May 29, 2001 09:52 p.m.):
For some reason, my Tbird 1.2 doesn't like multiplier 11x. If I set it @ 10.5x135 fsb it is rock stable. But @ 11x133, it won't even boot into windows !!
What type of RAM are you using to get 135mhz? I seem to not be able to get over 133mhz. I can run 11x133 all day, but the second I go to 134mhz, all is not good, windows goes nuts. Damn I want 1.5ghz!!

My RAM is the cheap generic PC-133 cas3 kind. I can run it @135fsb cas2 rock stable at default voltage, but above that it starts getting flaky and I would eventually get BSODs,lockups,etc... I suppose I could make it run faster and stable @cas3, but I rather leave it @cas2. With brand name RAM like Crucial, Micron,etc.. u should get better than 140@cas2.
Also don't forget each chip has its own limit. Once it "hits the wall", u won't get any more speed out of it, unless u get into some kind of xtreme or esoteric cooling ;-)