Unlocking 166FSB on AthlonXP

[pelly]

After doing a bit of digging...it looks as though it is entirely possible ( although likely difficult ) to have the processor run at 166FSB.

Looking at the data-sheet, we find there are two pins which determine FSB. ( FSB_Sense[1] and FSB_Sense[0] )

In order to achieve 166FSB, we must have the following:

FSB_Sense[0] : open-circuit. This could be left alone or covered with some non-conductive finish to ensure correct settings.

FSB_Sense[1] : Grounded-circuit. The document suggests using a 1 Kilaohm pull-down resistor before feeding the signal to ground.

http://pubpages.unh.edu/~seanp/PC/Pin-Out.png

You can connect FSB_Sense[1] ( Blue arrow ) to any of the VSS pins ( One is shown with Green arrow ) which will be acting as a ground. The trick is to knock the signal strength from FSB_Sense[1] down to keep signals clean. As such, a pull-down resistor must be used which will connect this pin to a VSS pin. Given the close-proximity to the hollow-space under the die, you could channel and insulate the leads of a resistor up to the connection of the two pins and then place the body of the resistor in the space under the die. This physical approach should bypass any blocker in the BIOS...

Anyone daring enough to fool around with this idea?
:p

Note: I nor nV News take responsibility for any fried CPU's...this should be done at your own risk.

Note: Some newer motherboards may have this pull-down resistor setup already incorporated within the grid...As such, the only thing holding people back is a block within the BIOS.

[Renzo]

Ok, it is very easy to unlock Thoroughbred. So you can use whatever FSB you want.

http://www.biwa.ne.jp/~yok/AthlonXP2200+-TEST/Athlon2200+.htm

It's even easier if you use copper wire bend to U and stick it on the socket to correct holes.

My Tbred is unlocked this way and I'm running it @ 1912,5MHz (153*12.5) as my MB (KG7lite) doesn't give higher multiplier and FSB is pretty much maxed out at 153MHz (memory can do 190MHz 2-2-5-2 1cmd and cpu can do 2080MHz with aircooling).

[pelly]

This is not just for the FSB in relation to the memory...I believe that trick just gives you the ability to alter the multiplier to gain the highest FSB for the memory...

This mod would be for the actual CPU FSB...without any dividers or alterations...

[werner_q]

Finally I registered for this forum. After reading the datasheet, I'm afraid that you are on the wrong trail. FSB_Sense[0] and [1] are clearly stated to be Outputs of the Processor. They *could* be used for the BIOS to *set* the correct FSB, in the same way that FID[3:0] are used to tell the BIOS what Multiplier it should set for the CPU. At the moment, the Pins are of no use, since there are (officially) no 166MHz FSB T-Bred's. Once again, as I see it: Somehow hardwired (Bridges on the Package, probably), the CPU tells the BIOS (via the Southbridge), what Multiplier and what FSB to set.

And, for the record: If something is labled as 'Output', never think of applying any Voltages, not even Ground.

P.S.: Regarding the Subject (Kill'em all): even though english is not my native tounge, I like to play with words. It's of course kilo-ohm, not killer-ohm - but maybe you were thinking of killing some T-Bred's ?

[pelly]

Thank you for pointing out that painfully obvious fact...I cant believe I somehow missed that... :eek:

Thank God it's Friday!

:p

[Cotita]

I have my athlon XP 1700+ unlocked running at 166*8.5=1412mhz with my epox 8k3a.

By the way in most motherboards you have to manually set the fsb to 133mhz for the athlon xp to run at full speed, which means its not recognized automatically. So you can set it at whatever FSB you want and as far as the processor can handle the higher speed it will work.

One more thing even if it would be possible to set a 166mhz fsb by the processor, (which is completely senseless, since you can do the same just changing the fsb manually in the motherboard anyway) the multiplier is still locked, so it probably wouldn't run unless you unlocked it and lower the multiplier.

[john19055]

I guess I don't see the meaning of what he is trying to say,I have my XP1900 unlocked and I run it at 10*167 all the time,but if I want to hit a 200FSB I have to run it at 9*200 on my A7V333 and when you first start in the BIOS when I first got it when it was still locked it still asks me what was i running a 1600 or a 1200 procosser.