a quick list of ideas for an FPGA-based computer architecture
-------------------------------------------------------------

- first implementation on Xilinx Spartan 6 (Papilio Pro)

hack processor
--------------

cpu
---
- 32-bit RISC-like
- run model based on registers and stack
- memory accesses of 8, 16, and 32 bits
- arithmetic operations: add, sub, div, mul, rem
- logical operations: not, and, or, xor
- branch operations: beq/bz, bnz, blt, ble, bgt, bge, bo, bno, bc, bnc, jmp/bra
- subroutine operations: cal, ntr, lve, ret
- stack operations: psh, pop
- i/o operations: in, out

mem
---
- 1 megabyte of RAM; 32-bit memory addressing
- memory mapped devices at high addresses (below 4 gigabytes in 32-bit version)
- optional mmu-unit for virtual memory

io
--
- 16-bit port address space for devices
- dma buffers, 64 kilobytes per device in initial configuration
- routing of memory mapped operations

gfx
---
- 640x480 default mode (16- or 24-bit pixels)
- framebuffer
- direct draw