In this archive you'll find these files:
  • AtomMemoryDecoder.vhd (VHDL source file)
  • AtomMemoryDecoder.ucf (constraints file, i.e. pin-assignment)
  • AtomMemoryDecoder.jed (JEDEC file for programming into the memory decoder CPLD)
  • AtomIoDecoder.vhd (VHDL source file)
  • AtomIoDecoder.ucf (constraints file, i.e. pin-assignment)
  • AtomIoDecoder.jed (JEDEC file for programming into the I/O decoder CPLD)
In this archive you'll find the files for running the Atom with a 4 MHz R65C02P04 CPU. It contains these files:
  • AtomMemDecoder4MHz.vhd (VHDL source file)
  • AtomMemDecoder4MHz.ucf (constraints file, i.e. pin-assignment)
  • AtomMemDecoder4MHz.jed (JEDEC file for programming into the memory decoder CPLD)
You'll also need the latest SYSTEM firmware for your firmware as this disables the printer functions if you have a non 4 MHz via. I haven't tested the W65C22S6TPG-14 yet, this is a 14 MHz version of the 6522.
This links to the GODIL bit file on Github.
This is the firmware for the PIC 18F4525. It contains boot loader v2.9 and AtoMMC2 firmware v2.A with support for random access files and SDDOS. Should be programmed with a suitable programmer. Later updates can be installed with the integrated boot loader.
This is the diagram of your new Atom after you have done the hardware mods. MK2 boards do not need those mods. Mk2p1 has the polarity of C37 corrected and changed the 74HCT24x to 74LS24x. These errors are in both MK1 and MK2 boards, but only applies to the silk screen.
A list of all components.
The gerber files that you need to order your own board. I used these files for
The Atom kernel, Basic, Floating Point Rom and AtoMMC2 filing system rom. The reset routine is patched to make extended resets possible and the AtoMMC2 rom is patched to work up to 4MHz. It also fixes the hanging bug after a cold reset. The original rom image can be found here.
This is a collection of utility roms. It also contains the original Atom DOS rom (can by loaded on demand). Simply unzip this file to the root of your MMC card and load the roms with *INIT. Atom DOS can be loaded by running *ATOMDOS.
The current version contains a beta of AtoMMC3 with Atom Tube support, 4 MHz and a modified version of JBOX which fixes the TURBO and WP commands and adds the XMS statement for XMS memory bank switching.
If you want to run BBC Basic on your Atom, this is your friend. There are two versions:
*ATBASIC2 which loads BBC Basic, but it's not persistent after a break
*BBC loads BBC Basic and survives a system reset. Return to the Atom by typing ?&BFFE=0 and press break. This version also supports BBCMMC 1.00.
An export of the KiCad schematic drawing.
An export of the KiCad PCB design.
Xilinx ISE project for CPLD firmware
All the files you need to modify the board for your own purposes and to order some PCB's at your favorite supplier.
The contents of the Atom firmware. It contains eight utility roms, AtoMMC system, AtomDos system and BBC Basic.

The downloads on this page will always be the latest versions. Updates will be announced via the StarDot forum.