Hardware
The FPGA design — SALLY/xt6502 CPU core, the ANTIC display pipeline, the blitter and HDMI scan-out, memory/register/pin maps, and the bring-up guide.
Atari-XT
A modern take on Atari computers, written with AI assistance, implemented on a single FPGA, and a compiler that targets them.
What is Atari-XT?
Section titled “What is Atari-XT?”Atari-XT (repo: fpga-xt) fuses two Atari lineages on a single FPGA: the name takes its X from the 8-bit XE line and its T from the ST / TT line.
The FPGA provides system-level services such as HDMI output, I2S audio routing to that HDMI, and a 2D blitter that is designed to be very useful when implementing GUI toolkits as well as games. There is also a 2D sprite engine that wcan work with any power-of-two sprite up to the 64MB of sprite-memory. The keyboard (and mouse) are implemented using USB from the FPGA ARM cores. System memory and a 1080p framebuffer live in DDR3, reached over AXI HP ports.
The “X” machine’s custom silicon is implemented in the FPGA fabric — a cycle-accurate enhanced SALLY 6502 with the ANTIC/GTIA/POKEY display-and-sound pipeline, as well as connections to the custom I/O ports of the 8-bit range, other than the keyboard and mouse of course, which are USB-based. Banked memory is backed by DDR via a page-cache so the system can run at top-speed as much as possible - meaning this CPU runs in triple-digits of MHz.
The “T” machine, a 680x0-family STe/TT, is planned. Unlike the 6502, this will be a software implementation on one of the Cortex-A9 ARM processing system (PS) cores on the FPGA. The idea will be to use a JIT compiler to translate the 68k opcodes into ARM assembly and run the binary “natively”. The resulting emulation is estimated at making it feel like a 50MHz+ 68030.
Underlying both chipsets is the host that ties them together: Running on the boot-A9 core, is a FreeRTOS-based multi-tasking environment that offers the SD filesystem, ethernet networking, HDMI out (with audio), USB-HID input (handled by a companion MCU), and a desktop environment with vended UI services (eg: GEM, available to both 6502 and 68k)
The system runs unmodified Atari XL/XE software, but isn’t bounded by 1979: expanded RAM is bank-switched into the 6502’s address space, the display is an always-on 1080p60 compositor in which each machine is just a scalable window, and a custom language — xtc (repo: fpga-xtc)— compiles modern, typed, class-based code straight to executables.
What this site covers
Section titled “What this site covers”Compiler (xtc)
The xtc language, its standard library, and the xtc/xta/xts toolchain — a C/ObjC-like language that compiles to native executable with bank switching as a first-class feature.
Operating system
The software half — multitasking and executable loading across hosted platforms, fast banked-stack context switching, the GEM/VDI blitter driver, and OS memory layout.
Project & status
Where the build is now — implementation status, the roadmap and future work, and design notes for in-flight subsystems.