Editing AMD Geode

[[Category:Projects]]
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 first video production.

See [[AMD Geode/Video 2]] for details on the second video production.

See [[AMD Geode/Video 3]] for details on the third video production.

== 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:

# A Raspberry Pi running [https://dosbox-x.com/ DOSBox-X]
# Thin client machines that used VIA CPUs
# Expensive single-board computers using a [https://www.vortex86.com/ Vortex86] chip
# Cheaper [https://www.86duino.com/?page_id=11 86Duino] boards
#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 [https://buy.advantech.net.au/Boards-Cards/Embedded-Single-Board-Computers-3-5-Single-Board-Computers-By-Processor-AMD-G-Series-Processor/model-PCM-9375F-J0A3.htm?country=Australia&token=637787139068984110&f=AUS 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 [https://www.advantech.com/products/todatasheet/D506B81F-3573-48AF-8F8A-DA57B0B22EBA PCM-9375 A3 specifications] shows these points that interest me:

* AMD Geode LX800 500 MHz CPU (see the [https://www.amd.com/system/files/TechDocs/33234H_LX_databook.pdf AMD Geode LX Processors Data Book] for more information)
* AMD Geode CS5536 chipset (see the [https://www.amd.com/system/files/TechDocs/33238G_cs5536_db.pdf 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.