Higher FSB => lower speed

B

baj

New member
Hi

Ive been doing some overclocking and observed a strange thing on the system in my sig. (3dmark amd Unreal Turnament made the same picture)

When I set FSB on 102MHz and Multiplyer on 8.5 gave 478x-3dmarks.
When I set FSB on 104MHz and Multiplyer on 8.5 gave 426x-3dmarks.
When I set FSB on 106MHz and Multiplyer on 8.5 the system won't run stable.

This is without OC'ing the Radeon.

My logic says that higher FSB should give higher performance. Should I try lovering the multiplier and increase the FSB ? Or should I just leave it as it is.

FSB: 102MHz
Multiplier: 8.5
Vcore: 1.775
CPU Speed: 868MHz 38-42°C
 
I have always believed you should kick the multiplier up until it gets unstable or refuses to post....then adjust the fsb to tweak from there. soundblaster's amoung other cards are very picky above 110. let us know...



A7V Bios 1006
9.5x103 - 978Mhz
 
When you alter your FSB you also alter your pci bus.So you could increase your FSB and actually decrease your pci bus.
The AGP speed is related to your pci bus.
EG-My mobo fsb 100 pci 33 fsb 124 pci 31 and many other settings. Your agp bus is pci times 2 ie.66mhz at 1x
 
is thunderbird on somthin when u increase yr fsb u increase yr pci because yr pci on a t bird or a p3 is either 1/3 or 14 depending on the fsb so if u have a 133 it is 1/4 to 33mhz if u have 100 fsb it is 1/3 to 33mhz do u get the picture
so if u are running at 110 fsb on a 1/3 pci bus u infact get a 136 pci bus
 
If you look in the mobo book for P3v4x you will see you can set you freq as follows.
cpu/sdram124 pci41
cpu/sdram75 pci38
cpu/sdram83 pci42
cpu/sdram67 pci33
103 / 34
112 / 37
133 /44
100 / 33
120 / 40
115 / 38
110 / 37
105 / 35
140 / 35
150 / 37
124 /31
133 / 33
So as you can see you can have the same freq with 2 different pci frequencies.
 
This strange behaviour when the FSB is changed after 3DMark2000 was started is well known. 3DMark2000 apparently check your FSB only once when it's started and bases some calculations on this value. When you change the FSB afterwards 3DMark doesn't "notice" this and thus delivers wrong values, e.g. the CPUMarks stay the same, regardless of what you set the FSB to.

Just quit 3DMark2000 and re-start it after changing your FSB and you'll see correct results.
 
When I changed my FSB from 100 to 104, I saw an immediate 100 point increase in 3Dmarks...haven't tested any other settings however.
 
Indiana said:
This strange behaviour when the FSB is changed after 3DMark2000 was started is well known. 3DMark2000 apparently check your FSB only once when it's started and bases some calculations on this value. When you change the FSB afterwards 3DMark doesn't "notice" this and thus delivers wrong values, e.g. the CPUMarks stay the same, regardless of what you set the FSB to.

Just quit 3DMark2000 and re-start it after changing your FSB and you'll see correct results.
Click to expand...

Actually I set the FSB through the soft-menu in the bios, so no 3dmark is running :D

Thunderbird said:

If you look in the mobo book for P3v4x you will see you can set you freq as follows.
Click to expand...

Dont have that manual, because I have an epox mobo. An so far I can see this is on when running 133MHz FSB, but Ok this could be the case.

I think I leave it at this, it seems to run very stable. Thanks for the ideas.
 
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