ASUS P3B-F modding
 

In the past couple of weeks I've been exploring some of my old hardware pieces I've collected thrue all those years I've been using a PC. The hardware has been taking dust for quite a while, but still works like a charm. The plan was to moddificate it the Xtreme way. This is what I had to play with:
- ASUS P3B-F
- Pentium 3 500 512kb cache 100MHz FSB
- ATI Rage Pro
- Some SDRAM
- a PSU



The ASUS P3B-F mainboard was a decent Slot 1 boad for it's time providing Jumperfree overclocking and hardware monitoring. My worst concern was to find a way to lock the busses I didn't want to overclock, anyone familiar with a PIII system will know what I'm talking about. I started exploring the Voltage Regulator since I had more experiance with those kind of IC's. The P3B-F uses the HIP6019BCB regulator from Intersil.



This IC contains 4 differant voltage regulators. The first one is used for the CPU core voltage. It is a basic buck convertor, you can see for example the 2 output legs for controlling the power mosfets, being UGATE1 and LGATE1. The trick we used to do so much when voltmodding is fooling the feedback part of the power regulator (FB1). The output voltage is being send back to the PR through a series of resistors. If we change the resistance of that circuit, the voltage at the feedback pin will change also, causing the power regulator to regulate it's output to a higher/lower voltage. But the thing is that there is a second feedback link attached directly between the IC's VSEN1 leg and the buck convertor output, my plan didn't really work out that well. The system wouldn't boot when attaching a resistor to ground on the FB1 leg. I had to do it a total differant way.

On the above picture you can see that I've marked 5 legs with red. VID0...4 are 5 parralel TTL compatible inputs connected to the CPU's Votage Identification legs. At boot the CPU sets a 5 bit TTL code to the VID input legs of the power regulator. This signal is then being converted to an analog signal, which is then compared to the VSEN feedback pin, 3 times:
1 -> to check over voltage (110%)
2 -> to check under voltage (90%)
3 -> over voltage protection (115%)
If the output voltage stays withing the marges, the power regulator will create a POWERGOOD signal, and if all goes well your system will boot.

So how did I voltmod my cpu core voltage? Imade put my own code on the VID legs ;-)
If the VID pins are being left open we set logical "1", if we being connected to ground we set logical "0". I desolderd the legs so that there was no contact with the mainboard's PCB. Next, I soldered 5 thin wires on them which lead to a 5 jumpers I've solderd on an extra PCB. The jumpers allow my to connect the VID pins to ground or being left open, and this way I can set whatever voltage the HIP6019BCB regulator allows me to (1.3V - 3.5V |D).



On the left side you can see that I added a easy voltage readout module, with on the right side my VID jumpers.



Next plan was to change the onboard 14MHz crystal and add locks to the clock generator, the ICS 9250CF-08.



The 48MHz and 24MHz singal for example is something that is not of any use for me to overclock it. Though some devices use this clock, and if I want to use them without isue I must find a way to lock those busses. Like Hirobo's Turbo PLL thingy I need to construct a circuit which outputs those singals and then connect them with my mainboard. Everything went so well... until I found out the really wasn't going to work. Have a look:



The pins I marked are the clock oscillators output legs for the signals I mentioned above. Though, when you have a closer look you see that those pins also have a second function, being frequency select pins. Yes, some times those output legs are actually being used is inputs for setting the FSB bus frequency. So, this means I problabe can't do what I did for adjusting the CPU core voltage, desolder and use my own created device. At the end of the road I didn't really suceeded in taking it the extreme way, though it's a fun way to experiance with stuff and to see how it actually works. If anybody has more things to add here, or correct some of the things I wrote down here, please do so. Until I find a way to reach what I really wanted, I stick you up with this last picture:

The new Hipro5 from belgium is here :D

Great work geoffrey!!!!

:wow:

Geoffrey, impressive is an understatement :ws:

Fantastic work, I'd like to learn some of these things from you :woot:

Thx guys :drink:

Time to crush the competition :p
http://www.hwbot.org/searchResults.d...inTotalPoints=

super nice work :D :woot: .

Now, don't shoot me if I say something completely stupid :) . But there should be a signal that allows a pin to switch between input and output. If you know what signal causes that, you could use it to switch to do some re-routing (when it should be output, use the external crystal (or whatever you want to do), when it should be input, let it be an input).
Right ? ;-)

If latency is not a problem, that could indeed work. I was thinking about a differant approach: building on own FSB generator, though your idea might be easier to do. Thx ;)

excellent Geoff. You have both the skills and the patience to do this !!

You needed a P3 board if I'm not mistaken? :D

Yeah ... socket 370 :D

Anyway, you made me switch on my p2 233 again. Cooling it right now with a abit chipset fan which is keeping it below 30°. Will have to find some mods for the mobo (AB BH-6) though

Lol, guess what I started bidding for this afternoon on TN forums?... a P2 233MHz :D
- some crazy dude got those booting @ 700MHz :no: -

They are great overclockers because of the 66MHz bus speed they require, just like the cely's.


Hey, ABIT BH-6 was also a pioneer of overclocking thrue the BIOS, and it has the same chipset, should be getting the same results.