AMD Geode

I have a board with an AMD Geode CPU for some light retrocomputing development. This page details it and whatever I get up to with it.

See AMD Geode/Troubleshooting for details on the troubleshooting process.

See AMD Geode/Video 1 for details on the video production about the troubleshooting process.

Motivation

For a while I've been searching for a small computer with these requirements:

• Runs real mode DOS programs
• Has a somewhat antiquated CPU
• Has an Ethernet card and DOS packet driver
• Doesn't consume too much power

The use case here is to run my Twitch DOS Bot I've been developing over the years.

After the searching I found that there were a few systems that could approximate this:

1. A Raspberry Pi running DOSBox-X
2. Thin client machines that used VIA CPUs
3. Expensive single-board computers using a Vortex86 chip
4. Cheaper 86Duino boards
5. An old Eee PC 1000HA I had

I eventually decided to go with option 1, a Raspberry Pi emulating DOS.

At least, until I saw an offer on eBay: a used Advantech PCM-9375F for only $50 AUD, which is over $400 less than new.

Why such a huge discount? Video output is broken. Which means you can't really do much with this machine. This at minimum would let me run by Internet-connected DOS bot and talk to DOS over a serial port.

I've also not had an x86 board with GPIO before, so that seems like something fun to play with.

I bought it on November 7 2021 and received it on November 12 2021.

Board specifications

The PCM-9375 A3 specifications shows these points that interest me:

• AMD Geode LX800 500 MHz CPU (see the AMD Geode LX Processors Data Book for more information)
• AMD Geode CS5536 chipset (see the AMD Geode CS5536 Companion Device Data Book for more information)
• Dual RTL8139 10/100 Mbps Fast Ethernet (second requires breakout board that I have)
• 5V power supply (12V needed for optional LCD)
• CompactFlash storage
• 3 RS-232 serial interfaces (only the main serial interface is given a port)
• 8 GPIO pins (you don't see x86 boards with GPIO often)
• No nopl instruction support (not documented)

Note that the IDE connector on the board is 2.0mm pitch, not the standard 2.54mm pitch most IDE cables use.

TODO: Look at board again and validate and clarify these specifications.

TODO: Add photos

Setup

For power I use a USB to Molex fan adapter. These come with the 5V USB connected to the 12V pins on the Molex connector in order to run a 12V fan at a lower voltage. With a little effort you can pry them out and put them in the 5V pins on the connector.

For storage I'm using a CompactFlash card. Nothing fancy.

For serial I'm using a DB9 null modem cable with partial handshaking. I tried buying one from eBay first but instead got a straight through cable instead. See my serial ports page for more information.