I have an old PC around the house, and i have no use for it at the moment. I was thinking (in the good old DIY (AKA Destroy It Yourself XD)) about scavaging the computer for whatever parts i could re-use. I have an arduino UNO, and often I find myself needing more sampling rate or faster computation and I thought that using that old pc's Pentium III processor might be a good idea. However, since I'm not that familiar with processors (only with arduino) I was looking for some pointer on how to make use of it. A few ideas I came with are:

  • An oscilloscope
  • A general-purpose meter (think home automation)

If you could give me some pointers about the feasibility (or even how to make something) out of those parts, much appreciated. Oh, and if you have any ideas for projects (preferably space-related since it's my major) please share them with me.

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    \$\begingroup\$ off topic question! Please read FAQ \$\endgroup\$ – Chetan Bhargava Dec 20 '12 at 6:27
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    \$\begingroup\$ From a practical standpoint, a CPU that old is so outclassed in price to performance ratio that it would be cheaper to buy new equipment, and recoup your costs in energy savings. Even the idle power consumption of old CPUs/chipsets can be poor comparatively. \$\endgroup\$ – jbarlow Dec 20 '12 at 6:58
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    \$\begingroup\$ Not without its motherboard. \$\endgroup\$ – Brian Drummond Dec 20 '12 at 11:37
  • \$\begingroup\$ Put it online to become part of the computing grid. en.wikipedia.org/wiki/… It's a way to help solve large problems. \$\endgroup\$ – Optionparty Dec 20 '12 at 15:37
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    \$\begingroup\$ A DSO (Digital Sampling Oscilloscope) is just a computer with a data-acquisition (analog-to-digital converter + memory) card. If you have the computer, use it. I fail to see how making your own motherboard (which is really all that you are describing amounts to) gets you anywhere. I'd focus on making a USB or PCI sampling card. That would be fun and useful! ...and you'd learn a LOT about signal acquisition, physics, and processing in the process. I used to make my students do exactly that. \$\endgroup\$ – DrFriedParts Dec 20 '12 at 19:25

It would be very difficult to use. It's a processor and not a microcontroller, thus you will have to provide everything :

  • external ram (is the ram controller inside on PIII? ) DDR are not that easy to implement.
  • Power supplies. I am sure it needs several voltages and you will have to follow a precise power up sequence.
  • Chipset? how do you interface something with the high speed bus of the PIII? There is no connections for FLASH, IOs, USB or something. Theses are generally done by the chipset. You could replace it by a high speed FPGA, but you need to have access to the PIII datasheet and bus specification to know how to interface with it.


It is feasible, but it's very complex.

In a personal scale from the easiest to the hardest :

  • Do something with an Arduino
  • Do something with a Raspberry Pi
  • Design your own circuit and PCB (not a clone of something found on the web)
  • Use a recent (not PIC16F84) microcontroller without libraries. Just bear metal programming using only the MCU datasheet and a good compiler
  • Do some tricky analog design
  • Do some simple FPGA design (including the board)
  • Design a processor platform from scratch (a new kind of raspberry pi)
  • Design into the RF world
  • Do advanced FPGA design
  • Try to use PC world busses from the low level (PCI PCIe BT USB2.0 ...)
  • Design a PC

Trying to do a kind of chipset to interface with a high speed bus of a PIII belongs to the end of my previous list.

  • \$\begingroup\$ p3 uses SDRAM (not DDR), in some rare cases even RDRAM. \$\endgroup\$ – Gunnish Dec 20 '12 at 11:01

If you still have the "old computer" in bootable condition use it in its entirety. Learn about MSDOS or FreeDOS and boot it up in that simple environment. Learn how programming used to be done on early PCs from times gone by and you can make strong use of your old computer chip. As others have said...it is hard to try to make your own motherboard for using old microprocessor chips. Even finding some of the necessary components to complement the old processor may be nearly impossible.

If your old computer is junk and not bootable then your best bet would be to junk it. Go around to garage sales and check places like Craig's list and you can find plenty of old computers that you may find in still bootable condition that can be had for very low cost. Spending very much money on it is extremely questionable because if you need more performance for some little project than your Arduino UNO can provide then there are plenty of other ready made "development" boards around that can meet that need far better than trying to re-use an old Pentium

The old Pentium may be much better used as a historical display like the one I made with magnets glued on it so it can stick to a metal surface...

enter image description here


To make the best use of it... Format the hard drive, load a legal OS, browser, etc, and donate it to a charity that can get it into the hands of someone who needs it.

Take a $100 tax deduction and use this to feed your electronics addiction.


Building your own motherboard for a Pentium III will be a difficult, if not downright impossible, task.

At least you will need to interface to RAM and a chipset that provides peripherals (e.g. I/O). This could be done with an FPGA but would be a major task - at least you will need the datasheet for the CPU. Also, power management and putting it all together on a complex circuit board (you will not be able to build it in a breadboard :).

If you really want to use it, get an old motherboard, RAM etc... and run a lightweight Linux OS on it - then you could use it e.g. as a server (which could be the most adequate task for it, since you considered home automation). But then, the price/performance or power/performance ratio might not be so great.


I think that a Pentium III is far away from being something useless. I have a few suggestions you can try out. But first, make sure you can boot the system, install some operating system, and run some stuff.

  1. This probably have some serial RS232 and parallel ports. You can do lots of good stuff with these: light control/home automatio, several control related stuff (motor, step motor, reading sensors, etc). Google is full of nice projects related. Just search!
  2. This can be a basis for a good old-style arcade PC. You have to install a lightweight operating system and fine tune it. The process itself is very fun. Then you can you install emulators and built a nice case around it.
  3. You can make this your laboratory for learning stuff: set down and try to install a usable graphical Linux environment. You probably won't get it right the first time, but I assure you you learn a lot in the process. Also you can use this as a testing machine for your software. You will them force yourself to write better (faster and less memory eater) code for your own tools.
  4. If you succed in getting the environment to work, try to setup a development environment: compiler, editor, debugger. Try to write some useful code with that.
  5. Try to transform this into a full featured internet router with every fancy stuff a router should have (and some it shouldn't).

if you want to do input and output using serial port, Read this up, I wrote this for people like you. https://sites.google.com/site/sandundhammika/usbserialport

Serial port itself have 2 inputs and 2 outputs which could be used as GPIO. And parallel port have many.

It's not simple to design a motherboard. Unlike original 8086 design now days we have super IO chips[even in PIII]. So you could not find IO controller chips like keyboard controller chip separately in your motherboard.

PIII uses FSB architecture in motherboards. This is how it look like. http://en.wikipedia.org/wiki/File:Motherboard_diagram.svg

In modern intel processors we use QPI (Quick path interconnect) , where you even can't find address and data bus lines in the chip. So no you could not have some fun of it.

Next difficulty is the power circuits inside motherboard. They are not simple as you think. Do you believe that intel processor draws around 60A of electrical current? Yes there is a step down bulk converter in your motherboard and that's why there are large capacitors and inductors are there.Even you can't play with these, because it's a 4-layer board and it's not even simple to remove a component and replace it like we do in television and PSU boards.

If you motherboard does have a ISA bus , then yes you could have some fun with it definitely. ISA bus is easy to interface and less configurations.


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