TODO:
        
A nice GUI
Gamma
CLK_70
DIP switches
Audio:
 CODEC
 PSGs (partial)
 SIDs
 OPL3
Timing:
 VIA timers/serial/handshake
PS/2 mouse
Mouse pointer PS/2 input (Pointer display works)
C64 keyboard
UART (RS232 or WiFi)
DMA interrupts
Buzzer (maybe implement with audio? could just ignore it)
F256jr status LEDs
Software reset
Hardware version info
CPU selection (6809, 65816)
Upload new flash
Boot from RAM
RAM expansion
Flash expansion
SDCard insertion interrupt

Acceptable lameness: (for now)

CPU: Not cycle accurate. Each instruction takes 1 cycle per byte read/written
     Closer, but real CPU takes more
DMA: Occurs instantly, BUSY is always 0
PS/2 keyboard: Output to it is always ACKed and ignored
NES/SNES: Scan happens instantly
SPI: Only direct support for SD card commands that the microkernel uses
PRNG: Always gives random numbers, all else ignored
      Won't match real thing without 25MHz FPGA cycle exactness anyway
IEC: Not implemented in emulator
RTC: Watchdog timer ignored