Adjusting FSB

[Kuroyama]

Stupid question, but how do I overclock the FSB?

I unlocked the multiplier on my 1700+ and can overclock it to an 1800+ no problem, and 1900+ is unstable. If I leave it at 1700+ and change the CPU clock I can get to about 138 without trouble, but anything above that and the computer becomes very unstable or Windows refuses to boot. Regardless of whether I change the CPU clock, the BIOS startup screen always shows the DDR-RAM at 266MHZ.

Everyone talks about 148 or other higher figures, so what do I need to do to make my computer run stably at a higher clock speed?

 

[Wuzup101]

I believe during the post the computer just reads the speed of the DDR modules. I know I have my SDR running @ 150mhz and it still reads as pc133 at that screan. You're still running at the fsb (138mhz x 2) however it won't show that on the screan. As far as hitting a higher fsb. I guess you might try turning the multi down half a digit and try upping it. However your ram might have hit it's limit at 138 depending on what it is. I also looked at your rig page...is this the rig you are talking about? The crucial DDR, assuming it's cas2.5, shouldn't have a problem with 138. You probably just ran out of room w/ the chip. You could increase cooling possibly, or try upping the fsb and droping the multi (which would lead to better memory and overall scores if you could get it to work).

 

[Kuroyama]

Yes, it's the rig listed on Anandtech. Tried lowering it to 1600+ and the FSB will go a bit higher, but crashes soon at even 145 :| . Think I'll just run it as an 1800+ without overclocking the FSB, until I can figure out how to increase the voltage more than +0.1V so I can do 1900+. It runs reasonably long at 1900+ and +0.1V, but I can't seem to increase the voltage more to make it more stable (do you know how to?).

 

[Assimilator1]

To test to see whether its your FSB or CPU speed is the problem select the lowest multiplier you can for the cpu.Then increase your FSB in 2MHz steps from the default 133 & see where it crashes.

I use Crucial PC2100 CL2.5 DDR RAM in my Asus A7v266e ,with the RAM timings at 2-2-2-6, 4way inter I can reach 153MHz ,but if I set precharge (I think it was called that!) to 6 I can't exceed 145MHz

What are all your RAM timings?

 

[Kuroyama]

The RAM timings are :

SDRAM cycle : 2.5
Bank interleave : 2
Precharge to Active : 2T
Active to Precharge : 6T
Active to CMD : 2T
DRAM Queue Depth : 4 level
DRAM Command Rate : 1T

Anything I should change here?

After playing around with settings yesterday I find the max I can get on my 1700+ is 10.5x and 150FSB, 11x and 142, or 11.5x and 136; above that and the computer spontaneously reboots after about 30 minutes of Sandra benchmarks. I did hear somewhere that the Enhance ATX-703 300W PSU on my Fong Kai case isn't rated for the 1700+, perhaps this is the problem?

 

[Assimilator1]

Try setting the Command rate to 2T ,I think that's what mine is ,there's minimal bandwidth loss doing this & it'll likely let you go to a higher FSB

Keep us posted

 

[rogue1979]

I know Crucial is rated at cas 2.5, but I would go ahead and set it on 2, even if you have to raise a few other timings you will get better performance. To test the fsb capability of your board, set you memory timings to crappy and lower you multiplier, see what you can get. I usually find that by setting the memory timings down from maximum just a bit, the fsb is able to run much faster. But if you have to use really decreased settings, then it doesn't do much good to raise the fsb. Use Sandra to benchmark your memory vs fsb and see what works best.

 

[Kuroyama]

Setting the Command Rate to 2T helped a bit. Is it better to go for higher FSB or higher CPU benchmarks? I can run stably 10.5x 150FSB or 11x 144FSB; under Sandra the former has 4.2% better memory benchmarks but 1% worse CPU benchmarks. Which is more important in practice? (I mostly run Folding@Home)

Could updating the BIOS make performance worse? I was getting 10x 158FSB holding up under Sandra for > 30 minutes, then I flashed the latest BIOS and now the best I can get is 154FSB, at 158FSB the computer won't even boot properly.

Would RAMsinks, or better cooling on the GPU or Northbridge (say, Crystal Orb) improve my overclocking?

 

[Assimilator1]

Re performance ,I know with SETI you'd be better off with the higher FSB option ,RC5 is the other way around ,I'm afraid I don't know about F@H ,best thing to do is ask the F@H guys in the DC forum section

Re BIOS ,flash back to the old bios & see if you can do 158MHz again

What HSF(size?) have you got on the Northbridge?

 

[Kuroyama]

I think I'll go for the higher FSB as the CPU speed difference is only 1%. Will look around for an old BIOS, although I'm not sure of the version I had. If I get back to 158FSB then I'll check the DC forum.

The Northbridge and GeForce3-Ti200 both have the very small HSF's that came with them (see here for a picture).

 

[Kuroyama]

Put the old BIOS back in. I can get 10x 158FSB CAS2 again with the old BIOS . The odd thing is, if I run identical settings under the old and new BIOS then the new BIOS has about 5% better mem stats under Sandra (CPU shows no improvement) . Is this sort of thing typical? Seems quite a big difference, but perhaps they optimized things for the AMD XP (old BIOS was first to accept XP processors).

Anyways, my best settings are to stick with the old BIOS and use the 10x 158FSB.

Maybe I'll try some intermediate BIOS's and see how they all compare.

 

[Assimilator1]

Maybe the newer bios has more aggressive memory timings? and thats why you can get a higher FSB with the older 1 & its scores lower

158 MHz is an amazing FSB btw