400 -> 533 FSB Xeon Mod

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For those of you with Xeons, the IWill DP533’s claim to fame has been its 133 MHz forced FSB jumper, which offers a way to overclock Xeons with a 100 MHz FSB.

On the other hand, there is another, universal method of doing this.

The Concept

(All screenshots come from the Intel Xeon datasheet.)

533 FSB Xeons were introduced in a new socket 604. This just added a pin to the socket 603 of the 400 FSB version. All the other pins are the same. This allows a 603 pin Xeon can be run in socket 604.

While there is a jumper on most all e7505 boards for a forced 100 FSB, there also is an auto setting. Automatic speed sensing requires some method to determine the speed from a CPU signal. If this signal could be modified, the motherboard could be “fooled” into running a 100 FSB Xeon @133Mhz.

Many might think the new extra Xeon pin might control this, but the extra pin in socket 604 doesn’t “do” anything. It has no electical characteristics, as shown below:

Mechanical Pin

That means its sole purpose is to to differentiate the two types of Xeon sockets.

The autospeed mechanism actually lies in two pins, named BSEL 0 and BSEL 1. The default setting (which produces a 400/100 FSB) is L and L, or 0 and 0. To create a 533/133 FSB, BSEL 0 needs to be changed from a L/0 to a H/1, as seen in this table:

BSEL Table

When you need a pin value to go from 1 to 0 (like you do in a P4 wire-wrap voltage mod), you need to add current to the pin with the value of 1. You follow the same principle to create a “1,” but instead of adding current to the pin, you must keep the current in the pin from getting to the motherboard socket. This entire mod is simply the isolation of BSEL 0.

The Testbed…

Matt Watras

I used

Supermicro X5DAE (e7505 chipset, dual DDR 266)
Xeon Prestonia 1.8 GHz

2 sticks of Crucial Reg ECC PC2100, 256 MB
60 GB Maxtor D740X-L
Visiontek GF3 Ti500

Antec EPS12v TruePower 550

Here’s what it looks like:

The System

The Mod…

Matt Watras

The Mod

Sorry, but no action shots. I forgot. 🙂

The set of BSEL pins are located in the bottom right-hand corner when the diagonal corners are facing towards you.

Here’s some diagrams to help. First, the overall pinout:


Let’s zoom in on the pins of interest:


Finally, from the table identifying Xeon pins:


At first, I tried to isolate BSEL 0 by painting it with a non-conductor, such as nail polish, with the point of a needle. However, I didn’t manage to paint enough of the pin to get an effect, and almost painted a few other pins as well.

After this failed, I did what any red-blooded American would do. I got violent.

OK, OK, I got very delicately violent; I snapped off the pin. 🙂

Using the same needle, I managed to get the pin in its eye; in fact, it is an almost perfect fit. With this control, I was able to gradually bend the pin back and forth, weakening it. After many twists, it snapped off.

I did slightly bend some pins in its general location, but using a tip from a previous article on here, I used a credit card to bend them back.

The Results…

Matt Watras

The Results

Here are “before” and “after” screenshots of WCPUID, and MBM





Look Ma, same voltage!


Hyperthreading also works at the overclocked speed.

Just in case you need a volt mod, here is the chart of pin configurations, as well as their locations:

The voltage chart:

Voltage Chart

The voltage pin names:

Voltage PinName

And finally, the voltage pins:

Voltage Pins

All you need to do is apply the same P4 wire wrap techniques to the Xeon.

While this mod may seem too complicated or risky, all you need to end up with a pretty substantial gain is a little patience following a slow, step-by-step process.

Have fun!

Matt Watras


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