Cores for the BBC or the Electron and even the Archimedes can be found for the following boards but no Atom in sight.
The MiST FPGA card by Till Harbaum and Lotharek emulates many retro-systems but not the Atom.
It cost is ~215€ with a case.
It has already many cores defined (Atari,Amiga, Apple II,ZX Spectrum,...) and even for the BBC. See the wiki.
I think it should be fesable to build an advanced "Atom core" by reusing pieces of code from the other cores.
And why not emulating an advanced 6502 with large memory map, colors and BBC basic ?
The card/case is already available for anybody.
- FPGA Altera Cyclone III EP3C25
Micro-contrôleur ARM AT91SAM7S56 for input/output management.
32 Mo SDRAM 16 bits.
USB controller MAX3241E.
USB hub TUSB2046.
VGA connector analogic.
4 USB ports host mode.
Analog stereo output.
Micro USB port for power (300 mA/5 V minimum and 400 mA/5 V with devices) and for flashing the microcontroller.
SD card slot.
Two DB9 ports for joysticks connection.
Two MIDI ports.
Three push buttons (reset the card, menu and the last one defined by the developer).
On / Off switch.
A jumper to activate flashing of the microcontroller via the micro USB port.
Two DIP switches (for firmware or disabling the FPGA).
ARM JTAG connector for development and debugging of the microcontroller.
FPGA JTAG connector for development and debugging of the FPGA.
ARM connector for debugging.
The above specifications are very interesting and normally allow re-implementation and enforcement of any machinery 16/32 bits.
They are better than the Minimig at memory and FPGA programming space. In the words of the designer of the project, the MIST card is powerful enough to enable the implementation of the Atari Mega STE at 16 MHz and the Amiga 1200 (AGA) to 28 MHz.