Tualatin In A BX Board

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The 440BX chipset has been one of the best and most long enduring motherboard chipsets to ever come out. It was released about 4 years ago and many people still use it today. The chipset is probably most noted for its stability and advanced-for-its-time memory performance. More than 2 years after its release, Intel released the i815 chipset as a replacement for BX, but the 815’s memory performance still couldn’t quite match the performance of the trusty old BX.

Up to now, the fastest CPU that can “officially” run in a BX motherboard would be a Coppermine Pentium III 1.1 GHz on a 100 MHz FSB. Intel purposely made the newer Pentium III’s and Celerons based on the Tualatin core incompatible with the old BX and original i815 motherboards by changing some of the CPU’s pin assignments and the voltage requirements.

This is too bad since the new Celerons based on the Tualatin core have 256K of L2 cache which is the same amount that Pentium III’s have. Unlike earlier PIIIs/Celerons, the Tualatin CPU’s support Vcore adjustments in 0.025V increments and the processor system bus operates at 1.25V.

For the BX, the Vcore adjustments in 0.025V is not really a problem since most newer BX boards allow 0.05V increments, which is really close enough. Furthermore, most newer BX boards support CPU core voltages down to 1.5V or lower while Tualatins use either 1.45V, 1.475V or 1.5V for the default voltage.

A bigger issue are the differences in the processor system busses. Pentium processors prior to Tualatin use AGTL+ which uses 1.5V signal levels. The newer Tualatins use AGTL with 1.25V signal levels.

If you want to read about the processor system bus further, please see page 11 of the Celeron datasheets which can be found here.

The specifications sheet for Tualatin Celerons state that AGTL and AGTL+ are incompatible. This may be true based on their design but in practice you CAN get the Tualatin CPU’s that need AGTL signals to work with motherboards that provide AGTL+ signals. I don’t know what the long term effects of running this out of spec would be so please do the modification that I will describe at your own risk. I have not heard of anyone killing their CPU by doing this but then again this modification hasn’t been around very long. around for a couple of months.

Once again, try the modification at your own risk since you will be running your processor out of spec and could void your warranty. I accept no responsibility for any mishaps you might have. If you can’t afford to lose it, don’t use it.


James Anderson


I guess that’s more than enough of the theoretical stuff. Now to the actual modification.

Some very dedicated and highly technical overclockers deserve all of the credit for this modification. I am simply using their findings and reporting my experiences. The person who appears to be responsible for the mod is NIGHTCAT from Taiwan. The other two pioneers I have run across who appear to have done quite a bit with the mod are EBC and CATCH22ATPLAY.

You will find more than enough reading at this thread at Overclockers.com’s forum, as well as this thread at Madonion.com’s forums.

I successfully modified the following: Asus P3B-F motherboard (Rev 1.04 with 1.06 BIOS), MSI 6905 Mater Slocket ver 2.3 (also did it with ver 2), and a Celeron 1.0A. There are numerous other combinations that may or may not work. Rather than asking me whether or not a certain motherboard/slocket combination will work, your best bet will be to root through the threads listed above.

Probably the most important variable on whether or not you succeed at the mod is the slocket you use.

I have not heard of anyone being successful with generic slockets. Having a brand-name slocket is no guarantee, either. I was unsuccessful with the mod using an Iwill Slocket II ver 1.0, but I believe someone in one of the threads was successful using ver 1.2 of the Iwill Slocket II. I have heard that people have been successful using the ASUS S370-DL.

I actually tried 2 different ASUS S370-133 units but was unsucessful with both of them. I also unsuccessfully tried a Gigabyte GA-6R7+. I was successful using the MSI 6905 Master slocket (ver 2 and ver 2.3) as well as with a ABIT Slocket III ver 1.1.

As for motherboards, I only tried the ASUS P3B-F and the ASUS CUSL2. This article will mostly concentrate on doing the mod with slot-1 boards, but the mod will also work with socket 370 motherboards as well. I may later try and add a socket 370 piece to this article. If you want to try the mod on a socket 370 board, I would suggest taking a look at the Madonion.com thread since they do discuss doing the mod with the CUSL2 and the Abit BX133.

To see if anyone else has been successful with your board, your best bet would be to check the above threads rather than asking me since I will probably have no idea.

The Task…

James Anderson

The Task

Briefly, this is what you have to do.

Look at the diagram. Make sure you have the CPU oriented correctly. Please notice that the top left corner of the CPU is notched (not totally square). (The other notched corner would be in the bottom left if I had included the entire diagram.)

You need to connect the 2 pins highlighted in yellow using a small piece of wire.

You then need to insulate the 3 pins in red so that they don’t make contact inside of the slocket (yes, one of the 2 pins you are connecting also needs to be insulated).

You then need to enlarge some of the pin holes on the ZIF socket cover.

I will go into more detail on each one of the required steps I have just mentioned.


James Anderson


Here is what I did to get the 2 yellow pins connected.

These pins are actually labeled AK4 and AK26. For a connector, I unfortunately had to hack up a good ATA-66 cable (with the 80 wire strands rather than 40 strands for the ATA-33 cable).

(Actually, you could try cutting off the end with the black connector and leave the blue and the gray connectors intact (it will be a little bit short but you still might be able to use it with your hard drives).

You will need to tear off one of the small strands and make sure that it is long enough to reach between the 2 pins. Make sure you give yourself a little bit of slack.

Some people have also used conductive paint to connect the pins together but I found this to be easiest for me.

For the path of the wire, please follow the earlier diagram as closely as possible. To fit the wire over the 2 pins, you need to strip away a small amount from each one of the ends and make a small loop on each end.

I find it easiest if I take a stick pin or needle and wrap the wire around the tip of the needle a few times (actually closer to 3 or 4 times) so that I get a real small loop.

If you wrap it around the thicker part of the needle (rather than the tip), the loop will end up being too big and won’t fit very snug around the CPU pin. Make the loop on both ends of the wire, as shown in the picture.

Connecting And Insulating…

James Anderson

Connecting And Insulating

Slip the loop over one of the pins. It will be very easy for the loop to come off so you will want to use a thin piece of electrical tape and tape the wire down right below all of the other CPU pins (don’t try to put the tape between the pins).

Then repeat this procedure with the other pin. After you tape down both ends, the wire should stay wrapped around the pins OK so long as your loop fits snug around the pins.

Now we will insulate those three pins highlighted in red two pages ago. There are various ways to do this.

Some people have yanked the CPU pins out (highly unrecommended). Others have pulled the metal contacts out of the ZIF socket. Yet others have even insulated the metal contacts inside of the ZIF socket with very small pieces of tape.

This is what I found easiest for me:

To insulate the pins, I hacked up some ATA-33 cable (not the ATA-66 cable we just hacked above, the older, thicker stuff) and pulled apart some of the strands to essentially make a plastic sleeve.

I cut into one of the ends to expose the wire, then took tweezers and pulled ALL of the wire out.

I took a stick pin/needle and put it into the other end of the ATA cable in order to make the hole large enough to fit over the CPU pins, then took the plastic sleeve and put it over each one of the pins.

You can probably get it about half way by hand but you will probably need to use tweezers to get the sleeve all the way down on the CPU pin.

Cut off any excess part of the sleeve after it fits over the pin using a razor blade. You might want to cut the sleeve off just a little bit above the CPU pin because the sleeves tend to get scrunched down when you force them into the socket holes.

Then take the remainder of the sleeve, stick the needle/pin in the appropriate end, and then repeat the procedure until you have insulated all 3 pins.

Here’s what it should look like when you’re done:

Widening Holes…

James Anderson

Widening Holes

The only step left is to slightly modify the slocket. You will need to take the top cover off the ZIF socket and make the appropriate pin holes larger.

You should be able to take off the ZIF socket cover by taking a very small screwdriver, go to the top part of the slocket and gently pry the side of the ZIF cover from the bottom. Be careful not to cut any of the traces on the PCB.

If this doesn’t work for you, you may need to take a small screw driver and carefully separate the socket cover at the four corners of the ZIF socket.

To make the socket holes bigger, I used two very, very small flat screwdrivers. I first used the smallest one to make the hole a little bit bigger, then used the larger one to make it even bigger.

You can find out if the holes are big enough by checking to see if the sleeves from the ATA cable will fit through.

You will want to do this for the three holes that line up with the pins that need to be insulated (make sure you get the orientation on the pins), as well as the AK26 pin hole connected to one of the other pins.

This is what it should look like.

Put the socket cover back on (make sure you also put the lever back on correctly). You should be able to hear the corners of the socket cover snap into place over the ZIF socket. Now carefully put the CPU into the socket. MAKE SURE THAT ALL OF THE PINS ARE LINED UP CORRECTLY AND THAT YOU HAVE ENLARGED THE CORREPSPONDING PIN HOLES.

You will have to force the CPU down into the socket. Try to get it as level as possible. Once again, make sure that the pins are lined up correctly or you may bend one or more pins.

You will undoubtedly be unable to get the CPU situated perfectly flat so just to do your best and get it as flat as possible.

Set the jumpers on the slocket. Make sure that you set the appropriate jumper to treat the CPU as a Coppermine CPU.

You can set the FSB jumper to your goal, but I usually just leave it set to “auto”.

For the voltage, set it to a level appropriate to what you need. I would recommend either 1.5V, 1.55V, 1.6V, or 1.65V. The higher you plan on clocking your CPU, the higher you will want to set the voltage.

Put the heatsink on and put all of this into your slot-1 motherboard.

Testing and Final Comments…

James Anderson

Final Words…

Testing And Final Comments

Hopefully you will turn the power on and hear that pleasant sounding beep indicating that your system is posting.

If you don’t, you may need to clear the CMOS. My suggestion for clearing the CMOS is more than just using the “clear CMOS” jumper. I would recommend pulling the power cord from the power supply and removing the battery for about 1 minute. Make sure you know all of your BIOS setting before you do this since they will be gone after you do this.

Below, you will see the POST screen of my Celeron 1.0A running at 140 FSB.

Please notice that the POST screen shows it as a Pentium II 1400 MHz but this is only because the BIOS does not have the new microcode for Tualatins. The CPU still functions without a problem despite this.

That’s it. I wish you the best of luck if you try the mod.

One thing I should discuss before ending is processor selection. If you want to hit 133 MHz FSB in your overclock, I would recommend either the 1.0A or 1.1A. The 1.0A is almost a sure thing at 1.333 GHz and you may be able to get up 140 or 150 FSB with some luck and some more voltage (probably 1.7V – 1.8V). The 1.1A has a very good shot at getting you to 1.466 GHz with a 133 MHz FSB and with some luck you might go further (not as likely though as with the 1.0A).

Keep in mind that your BX board will be running out of spec at 133 FSB so make sure that your AGP card and memory can handle this.

If you want to keep your board in spec at 100 MHZ FSB, you could try either the Celeron 1.2 or 1.3GHz and just run them at 100 MHZ FSB (these two processors are not as likely to hit 133 FSB so please keep this in mind). Intel will release a Celeron 1.4 sometime in the next month or so, and I believe this will probably be the last and fastest Tualatin Celeron.

Don’t forget that the Tualatin Celerons all have 256K of L2 cache, which makes them the equal to Pentium III’s. Intel slowed them down by running them at 100 MHZ FSB, but get the right CPU and you can fix that by running them at 133+ FSB.

Please direct any questions you have about the mod to this thread, and I or someone else familiar with this mod should be able to help you.

James Anderson


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