Programming x86-arch chips (CPUs)

[djkolumbian]

Before you decide to go off on a rant on me for how impractical it is, bear in mind that I have at least 3 different computers from 3 different eras (486, Pent II, AMD Ath) of the x86 architecture, and these things are doing nothing but sitting around gathering dust.

I wanted to tinker a bit with programming these chips and using them almost pseudo-MCU, just to learn a bit about how they're coded and a bit more about the architecture. I've studied it well enough to know key components of it, but never actually sat down and looked at an assembler.

Anyone got any resources for something like this? Again, these things are in 3 different stages of obsolescence and will continue to gather dust (and eventually be pitched). Might as well do some sacrificial, fun learning with them.

[johnwasser]

The firmware alone isn't enough for any significant software development.  You will need an operating system.  If you want to get close to the hardware you could install FreeDOS (freedos.org) or a Linux distribution (http://distrowatch.com).

[CrossRoads]

You don't program microprocessors directly. You program the (EE)PROM that is on their address bus.
Remember BIOS? The uP resets and runs code in the BIOS and from there jumps out to larger memory (CD, floppy, hard drive).
You also need RAM (usually DRAM) to complement any on-chip RAM.
Seems like first step would be getting some BIOS code written.

[djkolumbian]

You don't program microprocessors directly. You program the (EE)PROM that is on their address bus.
Remember BIOS? The uP resets and runs code in the BIOS and from there jumps out to larger memory (CD, floppy, hard drive).
You also need RAM (usually DRAM) to complement any on-chip RAM.
Seems like first step would be getting some BIOS code written.

Sorry for the delay -

First question to ask would probably be along the lines of how is the BIOS constructed? (i.e. is it written in an assembler, and what does it contain in an usual implementation?)

That being established, would it be possible to "use" a micro as a MCU provided it is socketed to the mobo with access to RAM/cache memory and peripheral/IO interfaces?

[CrossRoads]

1st question - I don't know. PCs have a lot going on with floppy, CD, hard drive, video, USB, etc. all being set up via the BIOS.

2nd question - sure. I put a 68020 on a board to set up memory and write to all the addresses to ensure valid error detection and correction values at each location prior to the system accessing the memory.