80386DX microprocessor board
Last updated: 2005
For learning purposes, but admittedly mostly for laughs, I decided to take an old 80386dx processor and build a little system around it: ROM, RAM, serial port(s), real time clock, possibly ethernet later on.
After a load of trial and error I decided to put the base system on one PCB, and the rest on another, which would sit right on top of the first.
Base system specifications
- 40MHz 80386DX, underclocked to 8MHz while developing
- 128 KB of static RAM
- 128 KB of ROM
- Dual UART
- Real time clock (DS1287)
- HD44780 LCD display interface
- Interrupt controller
There is no custom logic on this board (i.e. PALs). Every component is standard. As soon as I whip up some BIOS code, I'll make it available here.
Routing was a bit of a pain as I only had two layers to work with to put two 32 bit buses and a whole lot of other stuff on. The autorouter was useless, obviously. At one run it ended up with around 1000 vias. That's right, this board is manually routed.
After I check everything over, I will have the PCB made at pcb-pool.com. But I also still have to make an EPROM emulator, as I don't want to constantly move four EPROMs around.
Update: PCB is on its way! (March 7th, 2007) Looking back at the board, which I finished routing over a year ago, I pray that it will work lacking a ground plane.
The Eagle files (schematic, PCB) are up for download. Do not use these just yet, as it is a work in progress and they probably contain bugs. You can download them here.
Work in progress..